[olug] mail servers - can sendmail handle this?

Sean Kelly smkelly at zombie.org
Thu Sep 7 00:05:57 UTC 2006

Sendmail should be able to handle this, however I don't really like
Sendmail. I would highly recommend you look at the Postfix MTA. Postfix
has an extremely easy configuration file, and it also follows the Unix
model of having several small processes that work together to get the job
done. There are also several settings that let you tweak delivery
concurrency settings, so you can tell Postfix how many messages it should
handle at once.

Also, here are the acronyms for you:

MUA - Mail User Agent (pine, mutt, Outlook, Eudora, ...)
MDA - Mail Delivery Agent (procmail)
MTA - Mail Transfer Agent (Sendmail, Postfix, qmail, exim, Exchange, ...) 
MSA - Mail Submission Agent (/usr/sbin/sendmail)

So, when you send a mail in your MUA, the MUA uses the MSA to send it to
the MTA. The MTA then passes it on to another machine's MTA or or to an MDA
if it is to be delivered locally. The MDA dumps it in the mailbox, and the
MUA reads it. A lot of times, the MTA provides the MDA and MSA. For
example, Sendmail has a built-in MSA and MDA. Wee!

An example small Postfix main.conf config file:

     queue_directory = /var/spool/postfix
     command_directory = /usr/local/sbin
     daemon_directory = /usr/local/libexec/postfix
     mail_owner = postfix
     default_privs = nobody
     relayhost = ...
     myorigin = $mydomain
     alias_maps = hash:/etc/mail/aliases
     alias_database = hash:/etc/mail/aliases
     local_destination_concurrency_limit = 25
     default_destination_concurrency_limit = 10

I have another setup that looks at a PostgreSQL table for forwarding, and
my users can change the destination of their forwards via a web interface.
Postfix pretty much rules, in my book. It is extremely robust, easy to
configure, and pretty flexible.

On Wed, Sep 06, 2006 at 04:23:08PM -0500, Ryan Stille wrote:
> I recently setup a web server at work running CentOS (redhat enterprise 
> clone).  It comes with sendmail installed.  The only thing I changed in 
> the sendmail configuration was to send all mail through our dedicated 
> mail server.  I have very little experience with sendmail and had to 
> lookup how to do that.
> On one of our other (Windows) web servers is a web application that 
> sends out a large number of emails, 10,000 emails at one time, and about 
> 1500 emails that have a 500Kb newsletter attached at a separate time.  
> This is causing slow downs as the application server spools up the 
> emails and hands them to the dedicated mail server.
> The idea is to move this app to the new linux web server, and have it 
> hand off the emails to the localhost to be delivered.  My question is - 
> is a default sendmail installation up to this task?  I've pretty much 
> heard nothing but complaints about sendmail.  My only other experience 
> is with qmail, although I've never gone through a qmail installation 
> before.  If I need to switch to a different MTA (or is it an MSA?) I 
> would like to stick to one that can be installed as an RPM.
> Comments welcome.
> -Ryan
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Sean Kelly          | PGP KeyID: D2E5E296
smkelly at smkelly.org | http://www.smkelly.org

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