Hi,
I've been having this same issue for months now, I've tried following the instructions on the message twice, been through phonecalls lasting hours, have been promised resolutions after a period of 5 days and still nothing.
I've tried changing my password myself, virgin media staff have tried changing it and still I get the mailbox unavailable message, my emails have been unavailable to me since November 2020 and we are now nearly March 2021.
Please please can someone help me get my emails back?