Seems within the past month or 2 I have noticed my IMAP header updates have slowed down and sometimes time out. I am also starting to get a lot mail delivery deferred errors. Google apparently decides some of the mail I am supposed to receive is from bulk senders and stops delivery for several hours after a certain amount is received. Never had this problem up until about a month ago. The volume received from the blocked sources has not changed so Google must have changed something on their end.
I get email alerts from my servers and my server monitoring. That is what is being delayed which isn't good. Google doesn't have an option to whitelist unless you have paid gapps account. Adding the email addresses to the filters doesn't help.
Maybe I have to move back to using my own email server again?...Sigh.