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Tuesday, January 17, 2012

Linux EMail Services.

Typically Email System is divided in 3 Major parts.

1) MUA (Mail user agent)
2) MDA (Mail Delivery agent)
3) MTA (Mail Transfer agent)

MUA can be cosidered as mail client used for reading or typing mails for END user.
MUA can be classified in below categories
i) Web based E.g Zimbra, IMP
ii) GUI based E.g Thunderbird,Evolution(redhat 6 comes with this )
iii) Console based E.g mutt

MDA takes care of all receiving mail. it delivers it to a separate mail spool until the MUA picks it up for END user.This is usually refered as Local delivery agent as this makes more sense.
It works locally .It moves mails locally.When MTA transfer mail to destination MDA puts that in a mailbox.
MDA work typically involves sorting the incoming mails to directories, Identifying spam mail e.t.c

E.g .
There is only one MDA program which is  procmail.

MTA transfers mails from one to another servers until it reaches to its destination.


There are two Major type of Mail Programs used in Linux.
1)Sendmail 2)Postfix

Sendmail was the default mail program for Most of linux and redhat distributions but due to added features in postfix trend is now changing .RHEL6 comes bundled with postfix as default mail program.

To know what message transfer agent (MTA) you are using?
This can be done using following bash
#ps -ef| grep -iE "sendmail|postfix|exim|courier|james|lotus|qmail|xmail|postmaster"

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