Gmail blocking emails from GP

Note mass email addresses will get you flagged faster as spam than individual emails and yes too many emails to the same email address can get you flagged as spam -- then its a hassle to get that flagged state to not be flagged -- or enough flagged states can get you completely blocked which is even harder to get undone

Digests are generally the best route to take and not sending more than one or two emails per day to any single individual is best as well. Yeah it kind of depends on gmails criterion but most of the email handlers use pretty much the same criterion best thing to do is contact gmail support to find out what you can do since you are not spamming but sending emails at users requests -- which btw you might need to outline a bit better when they are setting things up -- I think there is a way to send a "test" message and have the user do something that keeps any subsequent emails from getting flagged as spam

Been I while since I worked with this kind of auto-emailing but that was pretty much the case a while back and I doubt it has changed much

I think a daily digest of a user's all notifications in one email may help this, and I'd also prefer that instead of so many emails.

If GP isn't sending mass emailings, so that isn't the issue here. I think it's really just a Gmail problem, not a problem with how GP handles emailing.

Again having worked with that -- I know some of what gets emails flagged as spam which I tried to outline -- the problem is if you get flagged as a spammer it is rather difficult (or at least it used to be) to get that changed and always required contacting the email handler

Yes, but if you've been flagged as a spammer, you are banned from servers. The problem isn't that emails aren't getting delivered at all, but that they are mostly either getting delayed or routed to spam.

Yeah I think now a days they have thresholds of some sort -- but I could be wrong on that one -- I know it used to be mostly black or white with a little bit of a gray zone -- it all depended on what got you flagged as there were different elements to it -- I think it had to do with potential spam versus sufficiently verified spam

Mine too, all delayed about 6 hours or so.

Delays are normally not anything to be concerned about as that could simply be processing issues and/or routing issues

Heck more recently I have gotten Text chat message on my phone like 24 hours later or more