smtp settings and sendmail.
i forgot to mention that i had one element missing from my nagios setup (besides check_mysql, which i still think someone needs to write a better version of): i haven't had sendmail running on my linux server in about two years, ever since i learned that optonline.net blocks port 25 (and i liked using my own server for outbound email).
today, i decided to change that all, except i didn't know what settings to use. i was fortunate enough to stumble upon this very cool list of smtp servers and my sendmail.cf file was updated in no time.
for some reason, i still needed sendmail-cf, so i simply ran:
# yum install sendmail-cf
on my fedora core 5 box, and when i ran
# make -C /etc/mail
everything started running perfectly. i already received my backlog of nagios emails that were queued since i installed the software, so i know everything is running smoothly.