[linux-elitists] Postfix vs Exim

Marc MERLIN marc@merlins.org
Thu Sep 19 20:55:44 PDT 2002

Ok,  this isn't  meant as  an Exim  rules Postfix  sucks (or  the other  way
around), I think both MTAs are very good and I'm trying to see which one is
better for each case.

I know exim fairly well, but I don't know postfix well enough to make a fair
comparison, so this is targetted at the few who may know both fairly well


- I know about the security model difference between exim and postfix.

- I do not  care much about which  one is faster at what,  they're both fast
  enough as far as I'm concerned

- I know  that because postfix isn't  monolithic like exim, and  that one of
  the prices to pay is that it doesn't do deduping (i.e. if a message is
  sent to you and an email alias, you get two copies). If postfix's secure
  module approach has other drawbacks, I'm interested to hear them

- I have been told that postfix can  do content filtering and bounce at SMTP
  time (like exim4's ACLs) and after data (like exim's system_filter).
  Confirmation would be appreciated

- I don't know  if postfix can do  fined grained ACLs like exim4  and do RBL
  rejects but only if the from  domain matches a string, the connecting host
  is in a  certain IP range, and  none of the receipients  is postmaster for
  instance. Is postfix that configurable?

- I don't think postfix can do SMTP callbacks or callouts like exim.
  Confirmation appreciated.

- I'm not sure that postfix can do the equivalent of exim's local scan or
  sendmail's milters. Confirmation appreciated

- postfix has an extensive lookup cache, which is a huge advantage over exim
  if you are doing  ldap lookups (ldap is slow, and exim  will not cache the
  lookup longer than the process runs)

- exim can  lookup users to  deliver for in ldap  or nis by  using getpwnam,
  using the C library and nscd, but if it does so, it cannot distiguish a
  non existant users from a connection refused.
  As a  result, you should  not use getpwnam and  libnss_* for any  MTA, but
  instead you should have the MTA behave as  a NIS or ldap client and do the
  query yourself.
  This is possible,  but a bit kludgy in  exim, and if you do  so, exim will
  not be able to cache the result.
  I've been told that postfix supports this better and will cache the result
  of the nis/ldap queries as if you were using nscd
  Confirmation appreciated.

- Both MTAs support TLS

- Exim is the only MTA I know that can create virtual aliases on the fly
  (i.e. mailman aliases)

- Can postfix,  like exim,  do mail  routing depending on  a file  (i.e. run
  procmail if  there is a  ~user/.procmailrc or run  vacation if there  is a
  ~/.vacation.msg, etc...)
- Does postfix  support complete header  rewriting (on all the  headers, per
  header and with regular expressions), like exim does?

- What other cool things can postfix do that exim can't?

"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems & security ....
                                      .... what McDonalds is to gourmet cooking 
Home page: http://marc.merlins.org/   |   Finger marc_f@merlins.org for PGP key

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