Hello all. I've been at this problem for about a week and am nearly
out of ideas. I've installed Mailman with basically the same
mm_cfg.py on 2 different machines besides the one I'm working on
(with the exception of hostname differences), and notification
messages get sent/received just fine. The 2 machines I tested on...1
of them was running Slackware-10.0, Gcc-3.3.4, Python-2.4, and stock
Sendmail (I think the version was 8.11.something). The other machine
had RH-8.0, Gcc-3.3.2, Python-2.2.1, and Postfix-2.1.4. The machine
I'm currently working on has Slackware-10.0, Gcc-3.3.4, Python-2.4,
and Postfix-2.1.5. However, on the machine I'm working on, there is a
slight configuration difference which I can't seem to find that is
making it so Mailman can't send any messages. The hint in the Mailman
log that I get that something is amiss is in smtp-failure:
Dec 22 12:49:55 2004 (29963) Low level smtp error: (-2, 'Name or
service not known'), msgid:
<mailman.0.1103737499.29900.mailman@lava-net.com> Dec 22 12:49:55
2004 (29963) delivery to igueths@lava-net.com failed
with code -1: (-2, 'Name or service not known')
Dec 22 12:49:55 2004 (29963) Low level smtp error: (-2, 'Name or
service not known'), msgid:
<mailman.0.1103737790.29954.mailman@lava-net.com> Dec 22 12:49:55
2004 (29963) delivery to igueths@lava-net.com failed
with code -1: (-2, 'Name or service not known')

I've asked both on the Mailman-users/Courier-users lists (back when I
was using Courier), and the closest I've gotten to solving this one
is that the connection to the SMTP server is somehow failing.
However, I don't understand how that could be possible, since I can
telnet to localhost port 25 and get expected behavior? In /etc/hosts
I have an entry for:
127.0.0.1 localhost

Does anyone have any idea where else I could look to see if anything
is wrong, whose missconfiguration might cause such behavior? Note
that on the system in question, regular sending/receiving of mail
works flawlessly. Also, does anyone know how/if I can run the
test_smtp.py script located in $PREFIX/tests to see if anything turns
up that way? Thanks in advance!

Sorry for the repeat post...I forgot to post my current mm_cfg.py,
which currently looks like:
DEFAULT_EMAIL_HOST = 'lava-net.com'
DEFAULT_URL_HOST = 'www.lava-net.com'
VIRTUAL_HOSTS.clear()
add_virtualhost(DEFAULT_URL_HOST,DEFAULT_EMAIL_HOST)