Objective 108.3: Mail Transfer Agent (MTA) Basics

  • The most common MTAs on Linux are sendmail, postfix, qmail, and exim.

  • sendmail, being the oldest MTA, has influenced current MTAs greatly. The other three popular MTAs all have sendmail “compatibility programs” to enable them to act as drop-in replacements for sendmail.

  • The file /etc/aliases stores aliases for inbound mail addresses; it can redirect mail to one or more users.

  • Whenever /etc/aliases is modified, newaliases must be executed.

  • Each user can forward his own mail using a .forward file, containing the forwarding email address, in his home directory.

  • Outbound mail that is trapped due to a network or other problem will remain queued; it can be examined using the mailq command.

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