Before the Forum Team arrive to assist can you check some things for them? Run the address through mailtester.com and see if the address is still valid. They can't guarantee that a Move & Transfer will work but that is a step closer. Also, you still need to pass security via private message - so be prepared to do that with information on both accounts.
And as advised, you would lose any emails attached to your current billing account.
Why not get a non-ISP email address that can travel with you when you move, and also offers better security and support!