I recently had a repair on my LG G3 that meant a factory reset. Since the reset I can't access my BT email from my app - this worked fine before the reset. I also couldn't access my email from a loan phone during the repair. I've since tried 3 further apps with no joy. The app people say it's BT's problem as do ee. BT say, because I can access webmail, it's not.
Various postings online say the problem can be solved by changing my webmail password - it didn't for me. I've tried manually setting up IMAP and POP but no joy. I usually get a message advising my login details are incorrect (when they're not) or a failed to sync to server message.
Don't know whether this is relevant by this morning I briefly got a message from webmail saying my credentials weren't recognised, then got in a few minutes later using the same credentials.
I'm no tech wiz, but 2 phones and 4 apps does seem to point towards BT...........or me.......