What is Mail Server on Linux ?
1. Basic Knowledge about Mail Server on Linux
- There are several TCP/IP protocols related to email. It’s 2 common protocols for receiving email are POP(Post Office Protocol) and IMAP (Internet Message Access Protocol). The SMTP (Simple Mail Transfer Protocol) is an important protocal for sending email.
- The most common SMTP email server on Linux is sendmail. The basic sendmail configuration file is complex.
- Postfix email is an alternative to sendmail that is problaly already installed in your Linux system. It’s successor to VMail and IBM Secure Mailer systems.
- We can not run both services at once, so you have to remove or disable one service.
- Postfix attempts to be fast, easy to manage, and secure.
- On Redhat, we can use redhat-switch-mail to switch between sendmail and postfix.
2. General Mail Services
- We are having 3 kinds of mail services: MTA (Messages Transfer Agent), MDA (Message Delivery Agents), MUA (Mail User Agents).
- An MTA is a server which sends email over network. Linux uses MTA agents such as sendmail, which uses SMTP Protocol to send email.
- An MDA is a mail processor. It takes messages from internet and stores them in servers or spools where mail readers (mutt, Kmail, Evolution ..) can read them.
- An MUA is an application which can helps you send and receive email though MDA and MTA. We are using MUA to send a message to an MTA as sendmail.
- 2 major protocols for receivingemail are POP3 and IMAP4.
- Sendmail is the most important email server on Linux, but we can use others: Exim, Postfix or Qmail.
3. Other Linux Mail servers
- Commercial Sendmail : Except free version, Sendmail also provide commerical version for enterprise. It can support many thousands of users. It’s available at www.sendmail.com.
- Exim : Exim MTA developed by Cambridge and is licensed under GPL. This can helps we to filter spam email on your mail system. It’s available at www.exim.org.
- Qmail : Qmail MTA is another alternative of sendmail. Qmail is used by an impressive list of Internet sites. It’s available at www.qmail.org.
- Smail : Smail MTA is easier to configure than sendmail. It can help us to protect “spoofed” messages. It’s available at www.planix.org.
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