I am getting the same error. but only on my primary email account, other 3 secondary accounts are working perfect.
( so I assume secondary accounts must be on different mail servers). I can't even login by webmail to access my emails, it just says invalid login or username.
I called the FREE fone number 0800 052 4315 to check out server outages. The recorded message says they will be carriing out work on all email storage servers between 1 am and 5 am on TUESDAY the 5th of April. It is now 20:45 on Tuesday 5th April and still no primary email service.
( maybe the techies should take less fag and coffee breaks)
Guess I will have to call that completely useless call centre in India again. Calls charged at local rates and you could be on the phone for up to 20 minutes listening to classical music just waiting for a real person to answer it.

bring back the call centres to the UK or Scotland or Ireland at least they understand the British people.