email delivery: postfix vs. login.conf?

[Aleksey Cheusov <cheusov%tut.by@localhost>]

Hi. My workstation running NetBSD is almost always highly loaded because
bulk builds run permanently. While I'm absolutely happy with system's
responsiveness I have one problem -- email delivery by postfix.  When I
fetch my emails by fetchmail (hyndreds of them daily) they don't appear
in /var/mail/ for a lot of days. I have a lot of log messages like the
following

   Jul 21 20:25:49 asrock postfix/local[11464]: 55E4BF0E76: 
to=<cheusov%asrock.chizhovka.net@localhost>, orig_to=<cheusov>, relay=local, 
delay=8849, delays=8849/0.26/0/0.19, dsn=4.3.0, status=deferred (temporary 
failure. Command output: local: fatal: execl /bin/sh: Resource temporarily 
unavailable )

or like this

   Jul 21 20:05:50 asrock local[494]: fatal: execl /bin/sh: Resource 
temporarily unavailable

I guess the problem is user's limit on a number of processes.

"ulimit -u" says "max user processes (-u) 768", this limit is set in
login.conf. A number of running processes is usually about 200-300, so
significantly less than 768. Does postfix use the default value 240 or
the problem is somewhere else? Ideas?

-- 
Best regards, Aleksey Cheusov.