I support a couple postfix servers that do a high volume of sending mail (not "direct marketing" :) for billing, invoicing and account update confirmations). On one machine, when the mailq is over 5000, things seem to get "stuck" where I need to restart postfix. If I don't, mail will pile up in the queue.
The current hack is to page my phone, then I ssh and restart it. Eventually I'll just cron it but it's annoying to figure out the root cause. Postfix version is 2.2.7. Any clues will be much appreciated, thanks.