This problem has possibly been posted before but I can't find a solution to the exact problem.

Windows 10 using Live Mail for email messages.  Has been working with no problems for years and years.  All of a sudden, I am getting the pop-up box asking for user name and password for the server, even though this has not been changed and there have been absolutely no changes to the computer and the "Remember me" box was ticked.

I can type in the details but it won't accept them and they are definitely correct.

Does anybody know of why this might be happening or an easy fix please.  I could remove the account and try setting it up again but there are some pretty important emails there that I don't want to lose.

Thank you.