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Re: Sendmail or Qmail ? ..

On Thu, 2003-09-04 at 01:43, Rudi Starcevic wrote:
> Hi,
> Sorry to bother you all with this repeat question.
> I've have searched around and seen plenty of opinions but I'd like to 
> ask again and get the latest from this list.
> Sendmail or Qmail ? That is my question.

I work at an ISP that used to use Qmail, but now uses Sendmail.  There
are several reasons why the switch was made, none having anything to do
with the "religion" surrounding either one.  The following is my
opinion, illustrated with some examples from my company.

First, scale is a consideration.  Once we began to grow our customer
base, our email volume began to increase dramatically.  Qmail queues
everything to disk, so the more mail you do, the more pressure you put
on your disk I/O.  The server running Qmail was always blocking while it
tried to keep up with the disk writes.  We had to decide whether to
spend huge $$$ on a big-iron server to handle it all, or to go cheap and
modular using some other MTA.  We opted for the latter.  We replaced our
single mailserver with four mail routing servers and two mail storage
servers, where customer accounts reside.

Sendmail uses RAM more heavily than Qmail, relieving some of the disk
I/O pressure, and improving performance under heavy loads.  In order to
go modular, we needed a directory service to tie it all together (so
that each mail router can reference a system-wide config, and figure out
where the mailbox is).  We chose OpenLDAP.  At the time (1999), Qmail
did not have LDAP support (correct me if I'm wrong).  Sendmail did. 
Even if Qmail did have LDAP support then, Sendmail's source was *much*
easier to dig through for the performance tuning we did.

Sendmail's milter plug-in system has also been invaluable when we
implemented server-side bayesian spam filtering, and as we work on virus

Today we are very happy with our Sendmail installation.  Debian and
Sendmail play very happily together, and with our modular setup we
process over 4 million messages a day with over 60,000 mailboxes.  Yes,
Sendmail has had several high-profile vulnerabilities, but with Debian
and apt, we were able to stay on top of it with little difficulty.  I
can see how Qmail could look attractive to a smaller site with a less
complex setup, but for us, Sendmail was the way to go.


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