I noticed getmail (pop3 connector) stops working after a while.
I solve rebooting the server, and then, after 3-4 days, getmail simply stops fetching the remote mailboxes again.
Nothing interesting in maillog or messages log files, it simply stops trying to fetch.
If I try to type the command (took from the getmail cron):
/usr/bin/getmail --getmaildir /var/lib/getmail/ --rcfile /firstname.lastname@example.org it just works.