E-mail is a kind of electronic means to provide information exchangecommunication mode Is the most widely used service on the Internet.Through the networkE-mail system , users can communicate with customers in any corner of the world at a very low price (no matter where they are sent, they only need to pay the network fee) and in a very fast way (they can be sent to any designated destination in the world within a few seconds)network user Contact.
E-mail can be text, image, voice and other forms.At the same time, users can get a large number of free news and special emails, and easily realize easy information search.The existence of e-mail greatly facilitates the communication and exchange between people and promotes the development of society.
According to the data, there are two versions of the world's first e-mail:
The first statement
The first email in the world in October 1969 was sent byComputer scientistA short message from Professor Leonard K. to his colleagues.
According to《Internet Weekly 》The first e-mail in the world was a short message sent by Professor Leonard K., a computer scientist, to his colleagues (the time should be October 1969). This message only had two letters: "LO".Professor Leonard K. is therefore calledE-mail Father。
E-mail
Professor Leonard K. explained, "In those days, I tried toCaliforniaThe university computer and another one located inSan FrancisconearbyStanfordComputer contact of the research center.All we do is log in from one computer to another.The way to log in was to type L-O-G.So we type L and ask the other party: 'Have you received L?'The other party replied, 'Yes.'Then type O and G.The system will be paralyzed before the other party receives the confirmation answer from G.So the first online message is' LO ', meaning' Hello! '"
In 1971, the US Department of Defense fundedAparnetIn the process of the project, a very acute problem has arisen: the scientists participating in the project are doing different work in different places, but they cannot share their research results well.The reason is simple, because we use different computers, and everyone's work is useless to others.They urgently need a method that can transfer data between different computers with the help of the network.Working for ARPANETMassachusetts Institute of TechnologyDr. Ray Tomlinson put one in differentComputer networkSoftware copied between and a stand-alone onlycommunication softwareThe function is merged and named SNDMSG (Send Message).In order to test, he used this software to send the first email on the Arpai net, and the recipient was himself on another computer.Although Tomlinson can't remember the content of this email, it still has full historical significance at that moment: email was born.Tomlinson selects the "@" symbol asuser nameThe space between the address and the symbol is rare and will not appear in anyone's name, and the pronunciation of the symbol also has the meaning of "being".The scientists of Arpanet welcomed this groundbreaking innovation with great enthusiasm.Their genius ideas and research results can now be shared with colleagues at the fastest speed - too fast to be detected.Many people recall that email contributed a lot to the great success of Arpanet.(This statement is also widely spread.)
development history
Although e-mail was invented in the 1970s, it was only in the 1980s that it was able to rise.The silence in the 1970s was mainly due to the fact that there were too few people using the Arpanet network at that time, and the network speed was only one twentieth of the 56Kbps standard speed.sufferNetwork speedAt that time, users could only send some short messages, and did not want to send a large number of photos like that;By the mid-1980s,personal computerThe rise of e-mail began to spread widely among computer fans and college students;By the mid-1990s, the Internet browser was born, the number of Internet users around the world surged, and e-mail was widely used.
A Brief History of Eudora
The first program to make e-mail mainstream was Euroda, written by Steve Donnell in 1988.Because Euroda is the first one withGraphical interfaceEmail forManagement proceduresIt soon became the main use in companies and university campusesE-mail program。
However, the status of Euroda has not been maintained for a long time.With the rise of the Internet, Netscape and Microsoft have successively launched their browsers and related programs.Microsoft and its developmentOutlookEuroda gradually declined.
In the past five years, the biggest change about e-mail is the rise of Internet based e-mail.People can maintain their email accounts on email websites through any networked computer, instead of using email only on their home or company networked computers.This email is sent byHotmailPromoted.Now Hotmail has become a popular website. Microsoft announced in August that the number of mail service users has reached 110 million.However, when Microsoft bought this website in 1998, it only spent 400 million dollars, which later made Shabir Buhatil, the founder of Hotmail, repent.
HotmailThe success ofcompetitorInspired, e-mail soon became a must for portal services, such asYahooNetscape, Excite and Lycos all have their ownE-mail service。
principle
Announce
edit
Sending and receiving e-mail
E-mail
The principle of sending and receiving e-mail on the Internet can be vividly described by mailing a package in our daily life: when we want to send a package, we first need to find any post office that has this business. After filling in the recipient's name, address, etc., the package is sent to the post office where the recipient is located,Then the other party must go to the post office to take out the package.Similarly, when we send an email, the email is sent by the email sending server (any one can), and the recipient server is judged according to the recipient's address, and the email is sent to the server. The recipient can only access the server to receive the email.
1. Email sending
SMTPIt is to maintain transmission order and regulationsMail serverThe goal of the protocol is to deliver e-mail reliably and efficiently.SMTP is delivery independentSubsystem, and can relay mail.
Figure 1 SMTP Communication Model
SMTP is based on the following communication model: according to the user's mail request,SenderSMTP establishes a two-way channel with the receiving SMTP.The recipient SMTP can be the final recipient or the intermediate sender.The sender SMTP generates and sends SMTP commands, and the receiver SMTP returns response information to the sender SMTP.
After the connection is established, the sender SMTP sends a MAIL command to indicate the sender. If the recipient SMTP approves, an OK response is returned.Sender SMTP ResendRCPTThe command indicates the recipient. If the recipient SMTP also approves, an OK response is returned again;Otherwise, a rejection response will be given (but the whole message sending operation will not be stopped).When there are multiple recipients, both parties will repeat this many times.After this process is completed, the sender SMTP starts to send the mail content and terminates with a special sequence.If the recipient SMTP successfully processes the mail, an OK response is returned.
If relay forwarding is required, if an SMTP server accepts the forwarding task but later finds that the mail cannot be sent due to incorrect forwarding path or other reasons, it must send a message of "mail cannot be delivered" to the SMTP server that originally sent the message.To prevent the error message from being sent circularly between two SMTP servers due to the possible failure of sending the message, the fallback path of the message can be left blank.
To maintain a message on a small node of the Internettransmission system (MTS, Message Transport System) is unrealistic.For example, a workstation may not have enough resources to allow the SMTP server and related local mail delivery system to reside and run continuously.Similarly, one is requiredpersonal computerThe cost of connecting to the IP network for a long time is also huge, sometimes even impossible.However, it is often useful to allow mail management on such a small node, and they usually support auser agent 。To meet this need, nodes that can support MTS can provide mail storage for these small nodes.POP3 is used to provide such a practical way to dynamically access e-mail stored on the mail server.Generally speaking, it means to allowUser hostConnect to the server to retrieve the messages that the server has staged for it.POP3 does not provide more powerfulmanagement function, which is usually deleted after the message is downloaded.More management functions are provided byIMAP4To achieve.
The mail server listensTCPOf110 portstartPOP3 service。When the user host needs to use the POP3 service, it establishes a TCP connection with the server host.After the connection is established, the server sends a confirmation message indicating that it is ready, and then both parties alternately send commands and responses to get the mail. This process continues until the connection is terminated.A POP3 instruction consists of a case independent command and some parameters.Both commands and parameters use printable ASCII characters separated by spaces.The command is generally 3-4 letters long, while the parameter can be up to 40 characters long.
IMAP4 provides a means to manage mail on a remote mail server. It can provide users with functions such as selectively receiving mail from the mail server, server based information processing, and sharing mailboxes.IMAP4 allows users to create arbitraryhierarchical structureIt is a folder for saving mail, and can flexibly move mail between folders, and organize your mailbox as you want. POP3 can only rely on the support of user agents locally to achieve these functions.If the user agent supports it, IMAP4 can even implement the function of selectively downloading attachments. Assuming that an email contains five attachments, users can choose to download two of them instead of all.
Similar to POP3, IMAP4 only provides user oriented mail sending and receiving services.The sending and receiving of mail on the Internet still depend on the SMTP server.
Composition of e-mail address
e-mail addressThe format of is composed of three parts.The first part "USER" represents the user's mailbox account. For the same mail receiving server, this account must be unique;The second part "@" isSeparator；The third part is the domain name of the mail receiving server of the user's mailbox to mark its location.
Address format
Announce
edit
User identifier+@+domain name
Where: @ is the symbol of "at", which means "at".
E-mail
The domain_name here is theidentifier , that is, the domain name of the mail destination to which the mail must be delivered.The somebody is the email address on the domain name.The suffix generally represents the nature of the domain name and the region code.The domain name is technically a mail exchange, not a machine name.
SMTP（Simple MailTransfer Protocol）: SMTP is mainly responsible for the underlyingMail systemHow to transfer mail from one machine to another.
POP(Post Office Protocol): Version isPOP3, POP3 is used to send mail frommail boxThe protocol that is transferred to the local computer in.
IMAP(Internet Message Access Protocol): Version isIMAP4, an alternative protocol to POP3, provides new functions of mail retrieval and mail processing, so that users can see the summary of the mail title without downloading the mail body, and can operate on the mail and folder directory on the server from the mail client software.IMAP protocolEnhances e-mail flexibility while reducingSpamIt is a direct hazard to the local system, and it also saves the time for users to view e-mail.In addition, the IMAP protocol can remember the user'sOffline statusNext mail operation (such as moving mail, deleting mail, etc.) will be opened next timenetwork connectionsIt will be automatically executed when.
In most popular email client programsSSLConnection support.
In addition, many encryption technologies are also applied to the process of sending, receiving and reading emails.They can provide encryption strength ranging from 128 bits to 2048 bits.Both one-way encryption and symmetric key encryption are widely supported.
characteristic
Announce
edit
E-mail
E-mail is between the entire network and all othersNetwork systemDirect to peopleInformation exchangeSystem, its dataSenderBoth and the receiver are human beings, which greatly meets the communication needs of a large number of people.
E-mail refers to the communication method of sending letters, documents, data and other information by electronic means.Email combinesTelephone communicationIt can transmit information as fast as the telephone, and make the receiver receive written records at the receiving end like a letter.E-mail system Also called computer-based mail message system.It participates in the whole process from the time when the mail enters the system to the time when the mail arrives at the destinationProcessing。E-mail can utilize not only the telephone network, but also any otherCommunication networkdelivery.When using the telephone network, information can also be transmitted during its off peak period, which has special value for commercial mail.By the central computer andSmall computerControlled for limited usersElectronic systemIt can be regarded as a kind of computerConference system。E-mail is stored-Forwarding modeThe gradual transmission of information on the network is not as direct and timely as the telephone, but the cost is low.
1. Sendmail mail system (supportSMTP）AnddovecotMail system (supportPOP3）
Sendmail can be said to be the ancestor of email, which has a history of more than 50 years so far.
Ben Dang's email is a typical representative
Electronic processing software
2. Based on Postfix/QmailThe mail system of.Postfix/Qmail technology is developed from Sendmail technology, with a history of less than 10 years so far.For example, NetEase Email's MTA is based on Postfix,yahooThe mailbox of is based on the Qmail system.
Exchange mail system is easy to manage due to its integration with Windows.It is the mail system with the largest number of users in the enterprise.IBM Lotus Domino has strong comprehensive functions, which are widely used by large enterprises. Postfix based mail systems require strong technical force to achieve, but the performance can be very high, and the security is good. At the same time, the software is open source and free of charge.
Select Mailbox
Announce
edit
Email Selection
In SelectE-mail serviceBefore business, we need to understand what the purpose of using email is, and choose according to our different purposes.
If you often contact foreign customers, it is recommended to use foreignmail box。such asGmail, Hotmail, MSN mail, Yahoo mail, etc.
If you want toNetwork hard diskUse, often store some pictures, etc., then you should chooseStorage capacityLarge mailboxes, such as Gmail, Yahoo mail,Netease163 mail, 126 mail, year mail, TOM mail, 21CN mail, etc. are all good choices.
E-mail
If you have your own computer, you'd better choose supportPOP/SMTPThe protocol mailbox can be accessed through Outlook,foxmailetc.Mail client softwareDownload the email to your hard disk, so you don't have to worry about the insufficient size of your email, and you can also prevent others from stealing your password and then peeking at your email.Of course, the premise is not to keep a copy on the server.I suggest doing so mainly from the perspective of security.
If you often need to send and receive some large attachments,Gmail,Yahoo mail, Hotmail, MSN mail，NetEase 163 mail, 126 mail, Yeah mail, etc. can meet the requirements very well.
If it is only used in China, thenQQEmail is also a good choice. An email address with a QQ number can let your friends send it to you through QQInstant Messaging。Of course, you can also use alias email.In addition, along withtencentThe acquisition of foxmail has greatly strengthened Tencent's technology in the e-mail field.So useQQ EmailIt should be very reassuring.
In addition, local mailboxes can be selected according to the region, such asBeijingFriends can chooseqianlong Email,GuangzhouFriends can choose21CN E-mail。
useCharge mailboxOur friends should pay attention to whether the cost performance of the mailbox is worth spending money to buy, and also to see whether they can pay for it in the long run188 Fortune PostAll very good, especially providing a variety of business cardsdesign schemeVery user-friendly, highly recommended.
You can also use the email provided by your own broadband service provider, such asTietong% of users can choose 68CN enterprise new speed mailbox, etc.
In fact, many people have a misconception about the size of attachments that support sending and receiving. Many people think that they must be large.In fact, in general, some data attachments sent are not more than 3MB. When the attachments are large, they can be sent through WinZIP,WinRARWait for the software to compress before sending.Mailboxes basically support attachments of more than 4MB, and well-known mailboxes have provided more than 10MB of space for sending and receiving attachments.One moreNot to be ignoredThe problem is that your email supports large attachments. Does your friend's email also support large attachments?If you can send large attachments and your friend's email does not support receiving large attachments, it is meaningless for your email to support any large attachments, so this issue is not important.
E-Mail
You can alsoIMInstant messaging software is used to select the mailbox. QQ mailbox is often usedYahooEasy to useYahoo Mail, use MSN mailbox orHotmailOf course, otherse-mail addressYou can also register as an MSN account to use it.Like to useNetease BubblesUse NetEaseMailbox 163。
Another important issue cannot be ignored.In the desktop operating systemWindows operating systemIt accounts for 90% of the current share.That is to say, 10% of our friends use Linux andApple OS。Because firefox browser can't support many java in web pagesscriptIt is difficult for novices to configure the browser, that is, they may encounter difficulties in accessing the mailbox through the WEB, so these friends must choose the mailbox that supports the POP/SMTP function, and send and receive mail through client software such as Kmail.Also use Linux andAppleFriends of Unix operating system do not recommend MSN mail and Hotmail, except that they do not support POP/SMTP, because they are from MicrosoftcompetitorIn order to prevent Microsoft from taking improper measures to block the sending and receiving of emails, it is better not to use the above operating systemsHotmailAnd MSN mailThere is no official MSN software of Microsoft on these operating systems, which can only be usedChat toolsThe plug-in of MSN implements some functions of MSN.
Select an email typically from“information safety，anti-spam。Anti killViruses, mailbox capacity, stability, sending and receiving speed, whether it can be used for a long time, mailbox function, whether it is convenient and refined to search and sort, whether the e-mail content can be easily managed, whether it is convenient to use, and various sending and receiving methods.Everyone can choose the most suitable mailbox according to their own needs.
2. The basic principle of e-mail is to set up on the communication network“E-mailSystem, which is actually a computer system.
The hardware of the system is a computer with high performance and large capacity.Hard disk as mailboxstorage medium , on the hard disk for usersstorage space As a user's "mailbox", each user has its ownE-mail。And determine a user name and password that the user can modify at will.storage space It includes three parts of space for storing received letters, editing letters, and archiving letters. Users use passwords to open their mailboxes and perform various operations such as sending, reading, editing, forwarding, and archiving letters.system functionIt is mainly realized by software.
3. E-mail communication is conducted between mailboxes.
The user first opens his own mailbox, and then sends the mail to be sent to the other party's mailbox by typing the command.Mail is delivered and exchanged between mailboxes, and can also be delivered and exchanged with another mail system.When picking up a letter, the receiver uses a specific account number to pick it up from the mailbox.
E-mailworking processFollow the client server model.Each email transmission involves the sender and receiver. The sender constitutes the client, while the receiver constitutes the server, which contains many usersE-mail。The sender sends the edited email to the post office server through the mail client program（SMTPServer).The post office server recognizes the address of the recipient and sends theMail server（POP3 serviceTo send messages.Mail serverIdentify the message stored in the receiver'sE-mailAnd inform the recipient of the arrival of new mail.Recipients send mail to customersProgram connectionAfter arriving at the server, you will see the server's notification, and then open your ownE-mailCheck your email.
Generally, individual users on the Internet cannot directlyReceive e-mail, but by applyingISPOne of the hostsE-mailThe ISP host is responsible for receiving e-mail.Once a user's email arrives, the ISP host will move the email to the user'sE-mailAnd notify the user of new mail.Therefore, when sending an e-mail to another customer, the e-mail is first sent from the user's computer to the ISP host, then to the Internet, then to the recipient's ISP host, and finally to the recipient'spersonal computer。
ISP host plays the role of "post office", managing the e-mail of many users.Per userE-mailIn fact, it is the account name applied by the user.Each user's e-mail mailbox occupies a certain amount of hard disk space of the ISP host. Because this space is limited, users should check and read it regularlyE-mailTo make room for new messages.
Tips
Announce
edit
Quick Find Messages
It is not easy to find the desired content in a large number of letters. The "Find Mail" selection allows users to search for messages in multiple folders to find folders orSubfoldersAny message in.Click the Edit menu and select Find Mail. Any of the following criteria can be used to find mail: who sent the mail, the subject or title of the mail, the text in the mail, etc.
Automatically add signatures
In OutlookExpress5, you can use the following methods to implement the automatic signature function:
(1) StartOutlookExpressAfter that, select the Tool Options command
(2) In the Options dialog box, click the Signature tab
(3) In the "Signature" tab, click the box before "Add this signature to all sent messages" to make it selected so that the automatic signature function will take effect
(4) In the "Signature" box, create a new signature nameText BoxType all personal information you want to add, such as name, contact address, phone number, etc
(5) If you want to add signatures automatically when replying and forwarding messages, you can click the box before "Do not add signatures to replied and forwarded messages" to leave it unchecked
(6) Click OK to automatically add a signature to your message the next time you create a new message.Of course, you can click the "Advanced" button to set a beautiful signature for each of your accounts.
Reject spam
In Toolsmenu barMiddle selection“Inbox Assistant ", click" Add ", the window is divided into two parts, the upper part is" Processing Conditions ", and the lower part is“processing method”。For example, if you often receive spam, if you want to stop receiving it in the future, you can select "From" in the "Processing Conditions" column and fill in the above address;Next, select "Delete from server" in "Processing method";After clicking "OK", you can see that in the description box, the description "will be deleted directly from the server, which achieves the goal.
Backup Address Book
In Outlook Express, the address book is very important. It records all yourpostal address, but for some reasonsReinstall the systemThe backup of the communication book is very important when the disk is formatted.Find a file named username.wab in the "C: windows ApplicationData Microsoft AddressBook" directory, where username is the registered user name on the computer.This is your address book. You can back it up in the specified path so that you can reinstall OutlookEx later?After presscopyGo to the original directory.
Write messages offline
Click the File menu and select“off-line working”, users can write emails calmly when they are not online.At this time, all the new messages sent are saved in the outbox window. Only when you press the "Send and Receive" button will OutLookEx? PressAuto ConnectThe Internet sends letters.
Solution to garbled code
The biggest trouble with email is receivingGarbled codeE-mail, this problem is especially serious for novices.OutlookExpress5 provides a method to solve the problem of garbled code: first select the garbled mail, click the View menu, point to Simplified Chinese in the Encoding command（GB2312）”That is, you can also point to "Other" in the "Code" command, where "Ala character", "Baltic character"“Central Europe19 characters, you can just click "Simplified Chinese (HZ)".Another method is: first select the garbled mail and click the right mouse button to open the mailshortcut menu, select the "Attribute" command;Then click the "Details" tab in the dialog box that appears, and click "Mail" in the lower right cornersource file... "button, the source file code of the email will be opened, so that you can see the content of the email.
Familiarize yourself with Outlook Express
In fact, Outlook Express has more than that.It is because of its multiple functions and greater convenience for users that netizens are obsessed with it.Now let's use the interface of Outlook ExpressTalk about it。
Outlook Express interface:
Outlook Express's interface is defined bymenu bar, folder list, content area, andstatus barFive major components.
Generally located inmenu barBelow, but the position of both can also be adjusted.The method is to drag the prominent place on the left and place it anywhere.The toolbar consists of some function buttons, which are common functionsShortcuts。
Click the button to open the new email editing window. In this window, as described above, fill in the address, subject, etc., write some content, and then send.
This button is mainly used to send and receive mail.You can use this button to check whether there is a new email or to send a written letter.
It is equivalent to amail list, used to store the communication address (i.ee-mail addressYeah).We can use the address book to storee-mail address, home and work addresses, telephone and fax numbers, digital IDsMeeting information, instant messaging addresses, and personal information, such as birthdays, anniversaries, and family members, make Outlook Express easy to retrieve.It can also be used to find users and business partners on the Internet.You can also store personal and corporate Internet addresses and link to them directly from the address book.Is it powerful?
Used to search messages and address book information.Click this button to pop up the window shown in the following figure.Enter the time of receiptSearch scope, and then start searching, and you can give the qualified messages.You can also search by sender, recipient, subject, attachment tag, and so on.This function is better for finding a large number of messages.
Folder list and content area:
It consists of two parts,mailing listArea and message preview area.The operation mode of folder list area and content area is the same as that ofwindowsExplorerThe operation of is similar.For example, click the inbox folder, and the content area on the right will display the mail in the inbox (mail is actually a file).Click the selected email to read its contents.
Status bar:
Located at the bottom of the Outlook Express window, it can display theworking condition 。
To send a message using an attachment:
What if you want to send a file, a picture, a sound file to your classmates?
Quite simply, there is a very important function button on the interface of editing new mail, that is, attach.There is onePaper clip！We use this paper clip to carry sounds, pictures and other documents.Please see the following picture:
After searching the computer for a long time, it was easy to find a better picture and click to send it.Has Kami received your letter?Let's check it out.Click Send/Receive, and the result comes out later,
Send successfully!
In fact, as long as it exists in the form of a file, it can be sent as an attachment.But please note that the file should not be too large.Send a sound file to the students to see how it works.
3. Use signs to prevent peeking
Outlook Express allows you to manage multiple accounts. If these accounts do not belong to you, your mail may be seen by others.Everyone has his own little secret.What can I do to keep this little secret?
Move the mouse to the logo in the content area, click the pop-up menu, and select Add New Logo.
The following screen will pop up:
Enter jimi.There is a password to ask when you start. This is very important. It can ensure that your email will not be seen by others.Click thischeck box, the password input dialog box will pop up.You can enter your easy to remember password here.Finally, click OK.
In this way, you must enter a password to view the mail of user migi.After starting Outlook Express, the main identification interface should be displayed, that is, the interface that every user can see. To change to your account, you can identify it from the content areadrop-down menu Select the switch ID on the.The switch identification window will pop up:
Enter the password and click OK to switch to your account.Note that the password must be correct.Computers only recognize passwords but not people.
The way to remove garbled code forever
Setting OutlookExpress5 can fundamentally solve the problem of garbled e-mail. The methods are: (1) Open OutlookExpress5, select the Options command in the Tools menu, and click the Read tab;(2) Click the "Font" button, select "Simplified Chinese (GB2312)" and set it toDefaultAfter setting, press OK to return to the Reading dialog box;(3) Click International Settings, select Use default encoding for all received messages, and then click OK to exit.Open all the emails again, and the Chinese emails will not be garbled.
Backup messages
Although Internet Explorer Outlook Express can export emails, it is a pity that only one email can be exported. If there are several emails, it is OK. The following method can be used.The specific steps are as follows:
(1) Open OutlookExpress and enter the mailbox to be backed up, such as the inbox
(2) Select the messages you want to back up.Press and hold the key, click the first and last email to select all;Press and hold the Ctrl key, click the desired message to select multiple messages
(3) Click "Forward Mail" with the left mouse button.At this point, the message you just selectedBe treated asAttachments, included in new messages
(4) In the New Message dialog box, choose Save As... from the File menu, and then choose a file name for this message——The above methods can selectively export mail.If you want to save the mail completely, go to the C: WINDOWS ApplicationData Microsoft OutlookExpressMail folder and back up all the files.
Don't use Word as the default messageeditor
Word takes a long time to start, takes up a lot of memory, and has a large mail length, which will inevitably increase the delivery time of mail. Therefore, it is better not to use Word as the default mail editor.
E-mail extension
Announce
edit
Multipurpose Internet Mail Extension
Multipurpose Internet Mail Extension（MIME, Multipurpose Internet Mail Extensions) enables e-mail to carry pictures, sounds, videos, etc. in addition to plain textBinary fileAgreement for.Of course, it requires that the sender and receiver of the email must have programs that can interpret MIME emails.
The basic idea of MIME is to add a structure to the mail bodyCoding rulesWill not beASCIIMessages are converted to ASCII text for correct transmission.Common MIME header fields include: MIME Version field indicates the MIME version;The Content Transfer Encoding field describes how to encode the mail body during transmission,Coding methodIt can be ordinary 7-bit or 8-bit characters, or 64 basic charactersCharacter encoding(Base 64 encoding) or quoted printable encoding;The Content Type field indicates the message type, such as text/palin, image/gif, video/mpeg, etc,SlashThe front is the main category, and the backslash is below itSubtypeAt present, there are 7 categories, including Text, Image and Audio（Audio）, Videoapplication programApplication, Message, Multipart, etc.
Base 64 encoding is a universalcoding method The principle is to use 4 bytes to represent 3 bytes of data.For such four bytes, only the first six bits are actually used in each byte, so it is not affected by the limit of only seven characters.The principle of Quoted Printing encoding is to use two 8-digit charactershexadecimalValue, and then add "=" to the front.For example, a document encoded like this usually has the following form:=B3=C2=BF=A1=C7=E5=A3=AC=C4=FA=BA=C3.
World Wide Web e-mail service
With the development of the InternetwebE-mail service for browsing mode.In this wayE-mailIt only provides more convenient mail receiving and sending services. E-mail transmission on the Internet still relies on SMTP, and these services usually provide POP3 messaging.With the World Wide Web e-mail service, users only need to use a browser to access the service provider's e-mail system website, enter a user name and password on its web page, log in to their e-mail box, and then they can process e-mail online.The advantage of the World Wide Web e-mail service is that users do not need to prepare special equipment or client software. As long as they can browse the Internet, they can enjoy many advanced e-mail functions provided by e-mail service providers.For example, customizable spam filters, temporarily setMail forwarding. Use when mail arrivesbeeperNotify users, and automatically reply to letters when users are on leave.
safety problem
Announce
edit
Safety knowledge
E-mailsafety problemThere are two aspects. One is that mail may bring to the systemUnsafe factorsThe second is the privacy of the email content itself.In this regard, I would like to share someE-mail securityTips on how to do this.
1. Security settings of the browser.
Taking IE as an example, it is recommended to upgrade IE to the latest version, and then click "Tools → Internet Properties" to enter "Security"tab Here, four different zones (including "Internet" and "LocalIntranet”, "trusted sites" and "restricted sites").The "Internet" zone can be set according to your own security considerations through "Custom Level".Although most cookies are secure for the system, setting them in the Privacy tab can properly protect your privacy.If you are worried about the disclosure of the letter content, you can set the certificate in the "Content" tab.
Due to the increasing automatic processing functions in software, we will see more and moreSecurity incidentsHas.MicrosoftOutlookThe "terrible auto fill function" in is an obvious example. It is easy to accidentally select a recipient close to the actual recipient when using the drop-down list.Similar in discussionTrade secretSomething like thatSensitive informationSuch operations can easily lead to various security events.
From a security perspectivee-mail addressIt is a bad practice to share with people who do not need to know.Without permissione-mail addressIt is also impolite to share with strangers.When sending e-mail to multiple people, you can select the recipient (TO) orCc(CC), so that all recipients can share alle-mail address。If there is no clear confirmatione-mail addressWhen it should be shared by all recipients, BCC should be used.In this way, the recipient will not know that there are other recipients.
4. Do a good job after reading.
If you send and receive letters in public places, the privacy of the content of the letter becomes critical.You can use the General tab of Internet OptionsDelete File(including allofflineContent)Clear HistoryAnd delete cookies.In addition, you can also go to the "Personal Information" column of the "Content" tabAutoCompleteSet, clear forms, passwords, etc.
useSSLConnection. The current two mail acceptance protocols and one mail sending protocol both support secure server connections.SSL support is integrated into most popular email client programs.After the message is encrypted, it is transmitted through a normal connection.For example, byGnuPGetc.Encryption softwareEncrypt before sending, Outlook can also.
2. Storage security
For encrypted messages, you can choose not to save the decrypted messages.Encrypted mail means that the sender encrypts the mail itself before sending it, not encrypted transmission.If the message itself is encrypted, encrypted transmission is not necessary.For unencrypted mail (which means that the sender did not encrypt the mail itself before sending it, and whether to use encrypted transmission is another matter), the storage security of mail is the same as that of other files, and the key point is to prevent unauthorized use.Of course, just as you can encrypt general files, you can also encrypt these unencrypted messages after they are received.
3. Recipient has received confirmation
The recipient may deny that he/she did not receive the email.In order to cope with this situation, different solutions have emerged, and there is no universally adopted scheme.MicrosoftMicrosoft of the companyExchange ServerDelivery Receipt is provided.Because it is the "recipient has received confirmation" sent by the machine, the recipient may delete the message intentionally or unintentionally.
4、Denial of service attacks?
In order to prevent a user from using e-mail (such as not allowing her/him to receive e-mail), a denial of service attack refers to sending a large amount of junk mail to the mailbox of the attacked user to fill the mailbox.In this way, the attacked user will not be able to receive those useful emails.This security concern has been addressed to a considerable extent.First, the mailbox keeps growing, and the other reason is that mail service providers have provided some filtering measures.Filtering measures sometimes treat useful emails as spam.Some mail service providers now use avatar mail to prevent outsiders from tracking mail accounts.
Security precautions
If the website cannot be accessed normally due to virus or hacker attacks, it will undoubtedly have a negative impact on the company's image, so perspectiveEnterprise websiteFirst, pay attention to the security precautions of the website.
In fact, many enterprises have realized the problem of website security, but for cost reasons, most enterprises are only on the websiteServer sideThe network firewall software is installed.althoughNetwork firewallFor commonMalicious virusandnetwork attack It can play a certain protective effect, but after all, there is no airtight wall. Any network firewall software inevitably has its own vulnerabilities. In addition, there are more and more Trojan horses and hacker software, and the update speed is faster and faster. It is no longer impossible to bypass the firewall and invade the system.Not to mention someWeb serverInstalledNetwork firewallIt is still an outdated version, and even has not been updated for a long time.If from theNetwork security protectionFrom an angle, adoptHardware firewallEquipment is undoubtedly the best solution. After all, more flexible and rich settings can increase the website serversafety factor。
2. Network security architecture
In order to save costs, some enterprises willNetwork sharingServerMail serverIt is integrated with the website server in one computer, but it was ignored after it was put into useSecurity precautionsQuestion.This does not mean that the server lacks e-mail filtering and virus prevention measures, but there are defects in the network architecture.Although most enterprises have configured a separate SMTP gateway anti-virus system, they do not take into account the security precautions for the enterprise's internal network. For example, the enterprise's internal mail has not been processed, similar to“CyberSky”OfMessage virusIt is likely to causeMail serverParalysis, thus affecting the normal operation of the website server.In fact, as long asMail serverConfigure accordingly, and make all the internalIP addressThe mail of is first forwarded to the SMTP gateway server for filtering, and then to the next forwarding channel (as shown in Figure 1).In general, try not to run multiple services in one computer as much as possible. After all, running one more service will increase a hidden trouble. The best way is to truly use a dedicated computer.
3. Artificial prevention
In addition,Website securityAn important part of sexual prevention is artificial prevention.Some companies do not have full-time staffnetwork administrator, web server sincePut into operationAfter that, few people paid attention to it. Maybe it will take weeks or even months to maintain it.This long-term attitude of indifference is also difficult to ensure the security of the website. If hackers break the firewall intrusion system during this period and transplant trojans or viruses into the server, it is likely to cause a large number of users browsing the website to be infected with viruses, which will directly affect the company's image and reputation.What's more, some network administrators turn the website server into their own network world and set it up without authorizationFTP, forum or othersnetwork service, occupiedsystem resourceNeedless to say, it provides an opportunity for hackers to invade the system.
Disadvantages of domestic enterprise websites
Many enterprises have invested considerable funds to establish their own websites, but over time, these websites often exist in name only, which can be summed up as follows:
1. The website has not been updated for a long time. Some enterprise websites have not been updated for several years, or even the company has moved but nothing has changed on the website, causing customersA lot of troubleIt is not surprising that the order falls into the hands of other companies.
2. The website will never have the content customers want.Many customers like to check and compare through websites, but some enterprise websites can provide too little information, and often these information can only be found from third-party websites. As a result, customers often contact enterprises that provide complete information first.
3. The information provided by the website is too much and miscellaneous, without focus, which not only wastes investment andoperating costs It is not easy for customers to find the information they need.So how is the website of a successful enterprise positioned?According to the survey, 26World Top 50076.9% of American enterprises have set up special columns of "products and brands";38.5% of enterprisesHome pageWith“Online services”Column, users can enjoy convenient and fast online handling services;96.2% of enterprises have a column of "Contact Us" on the homepage of the website. Users can directly contact with enterprises by clicking this column and feed back various user information to enterprises.In contrast, 75% of domestic enterprises that have also entered the Fortune 500 have set up product introduction columns, but few can provide online service functions, and only half of the websites have set up "Contact Us" columns.It is easy to see from the comparison of these figures that domestic websites do notnetwork marketingI don't know how to use the website for marketing, especially the actual role of the website is not good. The positioning of the website is just a primary product promotion site, which is formed with foreign countriesNetwork consulting, online orders, online after-sales, etcA dragoncompleteNetwork marketing serviceThere is still a considerable gap.
common problem
Announce
edit
oneMail serverUsed for mail transfer betweenTCPProtocol. Why are emails sometimes lost?
Mail serverBetweenSMTPTCP protocol uses TCP connection, which can ensure that messages are transmitted between mail servers accurately.However, due to the failure of the mail server itself, such as insufficient mail space, the mail can not be transmitted and will be lost.
2. Why does the sender user agent not send the message directly to the recipient user agent, but throughMail serverTo transmit?
Due to the limitation of the user's computer performance, it is impossible to run the program for sending and receiving mail, and it is impossible to run and connect to the Internet uninterruptedly, so the mail can only be temporarily stored inMail serverUsers can download letters when needed.
Spam
Spam does not have a very strict definition.Generally speaking, any email that is forcibly sent to the user's mailbox without the user's permission.
Before the emergence of spam, an AmericanSanford Wallace (or Spamford or "Spamford") set up a company to provide paid advertising fax services for customers of other companies. Because of the repugnance of the recipient and the waste of paper, the US legislation prohibits unauthorized fax advertising.Later, Junk Fu transferred the advertisement to email, and spam appeared naturally.
Message virusRefers to viruses spread by e-mail.It is usually embedded in the attachment of an email. After the user runs the virus program in the attachment, the computer will be infected.It should be noted that e-mail itself does not produce viruses, but is just a parasitic site of viruses.
E-mail bombE-mail bombIt is one of the oldest anonymous attacks. By setting a machine to continuously send a large number of emails to the same address, attackers can exhaustrecipientBroadband of the network.Because this attack is simple and easy to use, there are many attacksAnonymous messageAnd as long as the other party knows the specifice-mail addressYou can attack, so this is the most valuable attack means to prevent.
E-mail bombIt can be said that at presentnetwork securityThe most popular one inMischiefMethods, and these are used to make pranksSpecial proceduresAlso called E-mail Bomber.When the actions of a person or a company cause the dissatisfaction of a good doer, the good doer will attack by this means to vent his personal anger.This attack will not only interfere with the user'sE-mail system It can even affect the normal use of the mail systemServer systemThe safety ofNetwork systemAll paralyzed, soE-mail bombIt is extremely powerfulCyber weapons。
E-mail advertisementE-mail advertisementIt is a kind of electronic mailOnline advertising form, email ads may be allAdvertising information, or you may insert some useful information in the e-mail, which may be one-time, multiple or regular.Normally,network user You need to agree to join this email advertisement in advancemailing listIn order to accept this kind of advertising information, he will receive e-mail advertising, which is a model of licensed marketing.Those email advertisements received without permission are usually regarded as spam.
E-mail FilterThe information contained in the e-mail filter automatically classifies the received e-mail and puts it into the corresponding folder or mail box reading software.For example, all messages from a user's uncle Joe may be placed in a folder called "Uncle Joe".Filters can also be used to block or receive emails from a specified source.
Email DatabaseA specially formatted database that contains e-mail messages stored on your computer.After receiving/sending each message, each received/sent message is saved in the database.stayFull scanYour computer will scan this database.stayReal time monitoringIn the mode, all received and sent emails will be scanned forViruses。
Prevent spam
Method 1: set up your own mailbox“Good name”。If youruser nameIf it is too simple or too common, it is easy to be used as an attack target.Many people are used to using the pinyin of their names as their user names, but they are generally too simple to be captured by spammers.Therefore, when applying for an email address, it is advisable to have a more protective user name, such as the combination of English and numbers, and try to be as long as possible to avoid being harassed by spam.
Method 2: Avoid revealing your email address.When browsing the page, don't register your email address everywhere, and don't tell others easily. When friends leave email addresses with each other, you can use an alternative wayE-mailThe collection software can't identify it to prevent it from being attacked by spam.
Method 3: Don't respond to spam casually.When you receive spam, no matter how angry you are, do not respond. Here, "silence is golden", because once you reply, you will tell the spammer that your address is valid, which will attract more spam.In addition, there is another trick. In order to prove whether the e-mail address is valid, many spammers often say in an apologetic tone: "If you don't need our e-mail, please reply, and we will not send you any more mail". If you really reply, they will be fooled. The best way is to ignore it and put the sender on the rejection list;
Method 4: With the help ofanti-spamSpecialized software for.This kind of software is generally available on the market. For example, BounceSpamMail software can be used toSpammerReply and inform that the email address sent is invalid, so as to avoid repeated harassment of spam.McAfeeSpamKiller can also prevent spam and automatically reply "return" to the spammererror messageTo prevent similar emails from being received again.
Method 5: Use email management and filtering functions.Outlook Express、FoxmailandqqmailThey all have very good mail management functions. Users can filter mail by setting rules such as mail domain name, mail subject, source, and length in the filter.Spam generally has a relatively uniform theme, such as "promotion" and "sex". If you don't want to receive such emails, you can try to set the filtering theme to characters containing these keywords.
Method 6: Learn to use the remote mailbox management function.Some remote mailbox monitoring software can regularly check the remote mailbox and display information such as the subject, sender, e-mail size, etc. You can judge which is your normal e-mail and which is spam based on this information, so that you can directly delete the garbage from the mailbox, instead of downloading a large number of messages to your local mailbox every time.
Method 7: Choose a well served website to apply for an e-mail address.China has no legislation against spam, nor has it taken the lead in developing new anti spam technologies. The monitoring of spam mainly depends on the credit of Internet users andService ProviderFilter spam.Good service providers have more strength to develop their own spamFiltering system。
Method 8: Use YesService guaranteeOfCharge mailbox, the stability of the charging mailbox is better thanFree email。With the improvement of technologyNew servicesAt the same time, the emergence of the future two-way authentication e-mail system will also make spam away from people's lives.
