Sendmail problems
 

I can't send messages and keep getting 'host name lookup failure':

Aug 10 12:06:49 nick sm-mta[656]: h7AAbZYQ001059: to=<nick@xyphias.com>, ctladdr=<nobody@nick.home> (99/99), delay=00:29:14, xdelay=00:00:00, mailer=esmtp, pri=300308, relay=xyphias.com., dsn=4.0.0, stat=Deferred: Name server: xyphias.com.: host name lookup failure

Aug 10 12:08:28 nick sm-mta[797]: h7AB8SWW000787: to=<nylex23@excite.com>, ctladdr=<nobody@nick.home> (99/99), delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=30310, relay=excite.com., dsn=4.0.0, stat=Deferred: Name server: excite.com.: host name lookup failure

I haven't really used sendmail much, but I think it may be something to do with having a router (only thing I can think of as I remember it was working when we didn't) :/. I added the router to my /etc/hosts file, but still doesn't work.

Any help appreciated. Thanx.

IT sounds like a dns problem. Can you resolve any addresses from that machine? try:
ping www.linuxquestions.org
ping 64.179.4.146

Yep, pings work ok.