Postfix

[Gerald Combs]

Duane Attaway wrote:

> Postfix has a simple configuration file in english.  This may be good if
> sendmail's m4 macros seem scary.  But I didn't like how Postfix handled
> spam, accepting each mail even if it was an invalid user, then "sending"  
> it back as a bounce.  This was a problem as it amplified the bandwidth
> from spammers to users that didn't exist.  Postfix effectively DOS'ed my
> computer by crashing the memory to the end of swap.  I stopped updating
> the IP address to my attaway.net domain and went back to sendmail.  
> Sendmail seems much less memory intensive and behaves very well on my 32MB
> box with all my other applications.
> 
> Postfix's configuration file seemed rather limited in configuring how it
> was to handle different conditions.  Sendmail seems to be written from
> experience and does not quit.  Since my computer has been running for 247
> days without a reboot, I'm sticking with sendmail.  It works.  Postfix 
> didn't.

My experience with Postfix has been quite the opposite.  A few years
ago, when one of the Ethereal mailing lists hit several hundred, I
started receiving complaints about slow delivery times -- it would take
several hours for posts to reach some users.  The problem turned out to
be with Sendmail's queueing algorithm.

At that point I had spent a number of years administering Sendmail, and
  it was quickly losing its luster.  I switched to Postfix and haven't
looked back.  It delivers faster, it's easier to configure, and its
author responds informatively and politely to support requests.  As an
added bonus, the source code is well-written.

BTW, your "unknown user bounce" issue would most likely have been fixed
with

     local_recipient_maps = unix:passwd.byname

On most systems it's empty, which makes the smtpd process accept all
messages up front and bounce the invalid ones later.  Adding a recipient
map makes smtpd bounce invalid messages immediately.  This runs the risk
of someone brute-forcing a valid recipient list on your server, which is
why "bounce later" tends to be the default.  However, you can combine
the "bounce immediately" behavior with a configuration like

     smtpd_error_sleep_time = 270
     smtpd_hard_error_limit = 10
     smtpd_junk_command_limit = 5
     disable_vrfy_command = yes

to set up a pretty effective teergrube.

Dunno what to say about the memory issue.  Postfix uses several
processes (with different userids) to improve performance and security.
  On the Ethereal server the different Postfix processes take up 5 to 10
MB at any given time.  Sendmail would undoubtedly use less memory, but
my users expect performance and I expect security and manageability.