Overview of mail systems and email in Linux

1. Mail system role

MUA (mail user agent), MTA (message transfer agent), MDA (Message Distribution Agent), MAA (mail access Agent)

MUA: (Mail user agent): A user interface to an e-mail system, in most cases, a program that runs on a mail client.

Windows:outlook Express Foxmail

Lnux:thunderbird (Thunderbird) evolution

MTA (mail Transfer agent): Message transfer agent: The primary feature sends and receives messages, and reports the delivery of messages to the sender. mail servers can be divided into mail servers (SMTP servers) and accept mail servers (POP3/IMAP4 servers), depending on their purpose.

Windows: e-mail Service, Exchange Server,mdaemon,lotus notes Linux:sendmail (50%), Postfix,qmail

MDA (mail Delivery agent): Mail delivery Agent: After you go to the local post office, place the message in the user's mailbox. Can be a small program below the MTA, or it can be a single software such as Procmail,maildrop.

MAA: (Mail access Agent) (accept server) Mail Access agent: On behalf of MUA provides access to the message store and receive mail functionality of a IMAP/POP3 server, commonly used Courrier-imap, Dovecot.

——————————————————————————————————————

SMTP: (Simple Mail transmission Protocol) Easy Mail Transfer Protocol, TCP 25 port, Smtps

POP3, (Post Office Protocol) 3rd edition Post Office Protocol, TCP 110 port, POPs

IMAP4, (Internet Mail access Protocol) Internet Message Access Protocol, TCP 143 port, Imaps

This article URL address: http://www.bianceng.cn/OS/Linux/201410/45500.htm

Mine,mime: (Multipurpose Internet Mail Extensions) multipurpose, multifunctional Internet Mail Extension: Encode binary data in textual form and enable binary data to be sent by text protocol. Common coding Method: base64.

2. Commonly used mail server software

1). Commercial mail system

Exchange: Microsoft's heavyweight products, integrated with Windows series software products, collaborate better

NOTES/DOMINO:IBM Company's commercial email and office collaboration software products, features rich, powerful, provide cross-platform support

2). Open Source mail system

Sendmail: The most ancient, stable operation, but poor security

Qmail: Better implementation efficiency, configuration, management is also very convenient

Postfix: Compatible with SendMail, modular design, excellent performance in delivery efficiency, stability, service performance and security

Sendmail: Provide mail send service (SMTP)

Dovecot: Provide mail charge service (POP3)

Outlook Express: Client Tools for sending and receiving letters

3. Message Security:

1. Spam Anti-Spam SpamAssassin, authentication (address, account number), forward resolution and reverse

2). Virus ClamAV (drug search) characteristic code base

3). SendMail Mail Pager Mailscanner

SASL: (Simple Authorization secure Layer) Simply authentication Security layer protocol for providing authentication capabilities for protocols that do not provide authentication capabilities. Package: CYUS-SASL, Process: SASLAUTHD. Integrate Stmp,clainav (scan virus), SpamAssassin (Apache provides, scan spam) tools called caller (caller). Common caller Caller:mimedefang Mailscanner amavisd-new.

4. Mailbox Type:

MBOX all messages are placed in the same file, and new messages are appended directly to the file.

Maildir build a directory where each email is stored as a separate file in the directory

RedHat default use of the Mbox method, sendmail default use Mbox,postfix both support.

SMIME: Provides end-to-end message encryption and decryption protocol.