1) Make sure firstname.lastname@example.org
(the address we send from) is in your contacts list.
2) If it's getting sent to your spam folder, it can help everyone with this problem to remove it from spam and delete it normally.
3) You can also set up a filter in gmail to have it automatically skip your spam folder.4) No matter what, some of you use extremely dodgy sites to share pictures from, and notifications with those are not going to get to you, period end of story.
All major mail providers block these mails before they evaluate who it's getting sent to. If you're sharing naughty pics, it's best to first upload them to a trusted site like imgur or even Elliquiy here.
5) Similarly, Google in particular rate limits the amount of mail that gets sent to a given account from the same mailserver. Setting up a filter is helpful here but if you're setup to get a lot of notifications, you may hit this limit. At least one member (Beguiles' Mistress) does this regularly. This typically gets triggered when you'd get two mails in one minute.
6) Finally, the mail queue rate limits outgoing mail. During particularly active periods it's possible that mail gets delayed, but this shouldn't be for more than a few minutes. Sometimes the queue gets clogged for one reason or another (or something else is going on) and it helps to let me know if you're not getting mails, but I only have control over getting them to your mail host's server, not what they do with it once it's there.