Running exiqsumm a few times a day via cron is an excellent way to get a sense of what is normal for your mail queues and will help you pick up all sorts of problems. For example: Lots of mail waiting to be delivered to your local domain may indicate a local delivery problem like a broken local delivery agent (perhaps you just did a quick distribution update / upgrade and something important broke?), your mail volume has filled up, or some important, high volume user has filled up his mailbox and now his mail is just sitting on the queue? Lots of mail waiting to be delivered to domain example.com? Perhaps example.com's mail server is down, or a network problem has made them unreachable? Lots of mail waiting to go out to lots of different, perhaps suspiciously named, domains could indicate that your mail server is being used to relay spam. Here's how you use it: /usr/local/sbin/exim -bp | /usr/local/sbin/exiqsumm Exiqsumm will give you a nice tabular summary of what is sitting...