First, there is no guarantee in the world an email will ever be delivered.
Second, there is no guarantee whatsoever in which time an email is delivered.
During recent times there were two major delaying things going on, one is the split of traffic for low-pay and high-pay user, the other is fumbling on some email servers, part ordinary maintenance, part something else they won't talk about.
So, just relax and wait a few times before the surveillance net is fully armed again.