One for me, for future reference:
My mail server (qmail, plesk, ubuntu) has , for as long as I can remember, been delaying emails from a particular domain. Delays are usually a few hours – not enough to be a big problem usually, but certainly very annoying. Especially as the domain in question is used by most of my family.
I’ve finally had a look and discovered via the logs that greylisting was being applied, which indeed deliberately delays emails while attempting to resist spam in a smart way.
Once I added the domain to the whitelist, the delay has stopped. This is the command I used:
sudo /usr/local/psa/bin/grey_listing –update-server -whitelist add:*@domain.tld
Great! I’ve also noticed such a delay from other email accounts before, but I can’t find a way for the grey_listing program to tell me who it’s delaying so for the moment I’m turning the whole filter off. I can always turn it back on again. This command turns it off:
sudo /usr/local/psa/bin/grey_listing –update-server -status off