Delayed emails with TalkTalk is nothing new. I've experienced it many times. It's usually a problem when receiving, but I think I remember delays with sent messages as well. As per normal with TT, it's a waste of time trying to complain to their jokingly called "tech support" - all you can do is wait for it to be resolved. These issues are rarely admitted to on the official support pages, but there will be plenty of complaints on the forum...
TFP