What is Qmail Mail Transfer Agent
Qmail is a Mail Transfer Agent (MTA) that runs on Unix that is more secure replacement of sendmail program. Source code of Qmail is publicly available as well as its a free software.
The important feature of Qmail is:
Security: Qmail was first MTA that was built by keeping security in mind while design the architecture. That was not available at the time of sendmail.
*Performance: It can handle large email queue than sendmail its faster as well in terms of performance.
*Simplicity: Qmail is easy to configure and deploy
*. Innovation: Qmail has done some innovation as well like maildir format which creates seperate file for emails. Because there are several other MTAs that stores all emails in a single file. The other innovation was done in terms of wildcard mailboxes in which was first time where specific wildcards got generated that allows users to publish multiple email address for mailing list.
How to view Messages in the Qmail Queue
In order to view the messages on email queue. You need to login to server using SSH and should have root level permission to access these details
Linux command to list out all messages currently in queue:
Linux command to count the number of messages in the queue currently, type
To read the entire contents of an email in queue, including headers, type
find /var/qmail/queue -name NNNN| xargs cat | less
Where NNNN is 8 digit like
20 May 2014 04:05:50 GMT #1435166 517 <firstname.lastname@example.org>
If we want to see the detail any specific mail then need to write
find /var/qmail/queue -name 1435166| xargs cat | less
It will show complete detail of email like
email@example.com^@Received: (qmail 9874 invoked from network); 20 May 2014 04:05:50 -0400
Received: from 5e053af3.bb.sky.com (HELO psvobm) (192.168.0.0)
by ip-192-168-0-0.ip.secureserver.net with ESMTPA; 20 May 2014 04:05:50 -0400
Date: Tue, 20 May 2014 09:07:40 -0700
Content-Type: text/plain; charset=iso-8859-2