Alternatives to Sendmail

[sethg at ropine.com (Seth Gordon)]

   I'm setting up a new server, and thinking of replacing sendmail.  The two
   alternatives seem to be qmail and postfix.  Unfortunately, I couldn't make
   the last meeting about postfix.

   So I have two questions:  Can anyone list reasons why I should use one
   over the other?  They both seem more seucre and faster than sendmail.

I've used both on my home network.

Reasons to prefer qmail:

* Qmail looks like it can handle larger volumes of mail; a number of
  ISPs and other sites that handle a lot of mail (like, cough cough,
  Hotmail) use it.

* Qmail has a number of people and firms offering commercial support;
  I don't see any such support offered for postfix.

* The qmail system seems to use more mutually distrusting programs
  than the postfix system does, so it's probably better-protected
  against security holes.

Reasons to prefer postfix:

* Postfix configuration is closer to established Unix traditions.
  There's basically one configuration file, the package is installed
  where you would expect, etc.  Qmail breaks up its configuration into
  a lot of tiny files, it's installed in /var, and it depends on other
  djbware (tcpserver and daemontools).

* The author of postfix claims that qmail is vulnerable to certain
  denial-of-service attacks; if, for example, you connect to a server
  running qmail and keep feeding it RCPT lines, the server will keep
  collecting recipients until qmail crashes, rather than disconnecting
  after some set limit.

If I were setting up a new machine to handle my personal email, I
would probably use postfix.  If I were running an ISP, I would
probably use qmail.

   The other question is, can I install either of these apps without breaking
   sendmail?  If I stop sendmail and start up one of these apps then think
   better of it, can I just stop that app and start sendmail again?  Or will
   there be file clashes, etc.

The only filename clash is the name of the sendmail binary itself
(which is unavoidable, since so many other Unix programs assume that a
program called "sendmail" will deliver mail).  The documentation for
both postfix and qmail includes instructions for how to switch
gracefully from sendmail.  (Not so much about how to switch from them
*to* sendmail ... but I suspect that if you had to switch back and
couldn't figure out how to do it gracefully, the worst consequence
would be some mail queued during the transition not getting
delivered.)

-- 
"The conventional wisdom has it that when a program intended for multiple
users is to be written, specifications should be designed in advance....
Some people know better than this, but they have been silenced."
  --Richard M. Stallman
== Seth Gordon == sethg at ropine.com == http://ropine.com/ == std. disclaimer ==