i am operating an IMAP account on BT Yahoo using Mail on Mac both an iMac and MacBook Pro (same problem on both). This is the main account. My wife uses a sub-account of mine but doesn't have the following problems.
So every 2 or 3 days, around mid-afternoon, my account seems to stop working via Mail but is accessible via the web. I don't get any error messages at all but Mail is unable to access the account. For the rest of the day I can't access the account thru Mail but the day after it is working as if nothing had happened.
Any suggestions about what to do as it is very frustrating!
There are many such posts on the forum with no solution I'm afraid, it is just the flaky nature of the BT email system. If you are still on BTYahoo mail (you can tell by the yahoo branding in webmail) some posters have had success by logging in via the Yahoo site rather than the BT site and then logging out.