Do you have a problem with Blueyonder emails? One I was waiting for yesterday was delivered 4 hours after it was sent. Today, one I was waiting for took 4 hours. I had checked on the server from time to time in case it was a fault with Thunderbird but they were not showing there.
These emails were on different mailboxes.
There may have been more that were delayed but I would not notice unless it was something that I was expecting.