[geeks] thoughts on SMTP

[Jonathan C. Patschke]

> > Anyone who runs a mail server which handles any volume of mail will
> > be running a mail server which is relatively busy, and without
> 
> 0.75GB per day. Not that much but it's "any volume", and not 
> inconsiderable. The load on the servers due to mail is insignificant.

$PreviousJob moved approximately that volume of mail on a dual-proc SPARC
10 for the longest.  They -just- upgraded to a U1-170E.  On the SS10, the
load held at about 0.40.  On the U1-170E, the load hovers at about 0.80,
but we also added McAfee VirusScan and vilter to the mix to stop the
lusers from opening/sending virus-laden attachments.  The servers hit 2.00
and 6.00 during peak hours, respectively.  vilter+McAfee -really- strains
a busy box, it seems.

It's worth noting that said box was running a crapulatious webmail program
that used MySQL as a backend, and that lazy-ass tech support were
referring more and more new lusers to -it- rather than teaching them how
to set up Outhouse Explodes.  So, the webmail app took quite a spanking.

So, I'll second the observation that mail servers that:
   1) Aren't running anything else.
   2) Are sending mail either to other servers or to very simply-formatted
      inboxes (such as mbox[1]).
   3) Aren't running software raid or any other software that causes I/O
      activity to influence CPU activity.

probably are running at fairly light load averages, with almost no CPU
consumption, and probably could stand do to compression.  At least, that's
what my evidence leads me to conclude, and I'm sticking to it. :)

--Jonathan
[1] Yes, it sucks for IMAP and anything that does anything complicated to
    mail, but it's perfect for SMTP spool-in/POP3 spool-out, and it's
    ultra-low processor overhead.