On and off over the past year or more I have found I am unable to access my btinternet.com email account using Outlook 2016 in my desktop or my Windows phone. The error message was to the effect that the server was rejecting access because my account details were incorrect. I had no trouble accessing using web mail with the same account name and password as I had configured for Outlook and my phone. To begin with I messed around trying to change my password, and ringing the help desk. The former made no difference, and any mention of Outlook to the help desk ws met with a 'we don't support Outlook' reply.
I now find that so long as I am patient and wait 24-48 hours all is miraculously restored. I am guessing but perhaps the problem is resolved when a mail server is rebooted, or the like.
My latest outage was from lunch time Monday to sometime overnight Tuesday (30-31 Jan). Anyone got an idea what is going on?
As you are aware there has been issues with email clients being unable to logon happening over many years. There has never been a solution posted other than just "keep it till it gets better" as it usually resolves it self in a day or two. The other advice is do not change any settings or passwords as that can cause its own problems.
If you search the forum you will find a number of threads about problems with Outlook and other email clients.
I have listed just a few of the threads.
For some reason it was only recently I thought to check this forum to see if I was alone. Clearly there are many people who have been suffering from this for a long time. Between them all there should be more than enough diagnostic information to track the cause down.
I sugget we raise what used (and may still) be known as 'Chairman's Cases', the highest form of escalation I am aware of.
Wirte using snail mail directly to the BT Chairman - Jan du Plessis, BT Group plc, BT Centre, 81 Newgate Street, London EC1A 7AJ
I suggest using this route rather than following the compaints procedure published on the BT website as that clearly does not work.
Points that appear common to everyone are:
If sufficient people do this there is a chance it might be taken seriously, but don't hold your breath...