I have two gmail accounts in Apple mail (a work account and a personal account) and for some reason my work gmail keeps having issues syncing/loading new mail. Almost every time I start up my computer any new emails that are supposed to be in my work gmail account are not there (and sometimes old emails are not there). Then usually, after maybe a few min to up to 30 min, they start loading in chunks until they are all there. When I check my personal gmail at the same time, this issue isn’t happening- all my new emails to my personal gmail come in just fine. I have checked my IMAP settings and everything seems right on my work gmail, and the wifi is fine. I have also rebuilt my inbox a few times, no luck fixing the issue. Does anyone have any ideas/possible solutions to try?
Krista, have you tried going to Apple Mail > Settings (or Settings > Internet Accounts), deleting your work Gmail account; then via its user name and password reinstalling that account?
Doing this should fix things! 
Hi Bill, I did try that but unfortunately that doesn’t seem to fix things. Thanks for the suggestion though.
Krista, ouch! But I suspect then that this delay involves Gmail’s implementation of IMAP (which is unorthodox). I experience delays like these between Mail on a Mac and Mail on an iPad Pro or iPhone.
I’ve six accounts in Apple Mail, one of which is Protonmail bridged in, with four Gmail accounts, so Mail is worked fairly heavily. One of the Gmail accounts is ‘storage’ with many folders. I notice the kind of delay you’re speaking of when I copy out of a ‘daily’ Gmail account into the storage one on a Mac and then, sometimes a couple of hours later, go to this account in Mail on the iPad to read a recently stored mail which simply isn’t there. And sometimes doesn’t arrive for 24 hours.
Photos across iCloud can behave in a similar way – so I concluded some time back that I’m experiencing IMAP delays up to Gmail’s cloud. The way you’re describing this rather confirms it!
Years ago before Apple applications were stored on ‘sealed’ system volumes – with everything running off a ‘snapshot’ at boot up – apps like Mail could become damaged on the drive, needing to be reinstalled via package utilities like Pacifist – but those days are well gone. I don’t know enough about the ins and outs of IMAP to understand the structure of the delays we’ve experienced – perhaps someone else here does?
But I think something like this is all it is… 