I have a number of clients who are (sometimes) unable to send and receive due to Unrecognised Username or Password
and an associated PopUp although the credentials (and other settings) are absolutely correct and frequently work. It is always possible to access mail online using the same credentials at the Yahoo site.
I have lost count of the hours I've spent re-explaining and demonstrating the problem to different BTInternet support people over the last year but am glad to say that my latest client's issue has just been escalated to Yahoo Level 3 Support!!
I have been told various things over this last year including:
There was a major issue with Yahoo which lasted at least 6 weeks late in 2011 which prevented many users of many email clients being unable to access mail due to the PopUp.
If a second device (a phone for example) is configured to access the same Yahoo mailbox this can cause other clients (Outlook or Windows Mail for example) to be unrecognised due to some kind of contention.
There is no point in using a local mail client these days - just use webmail
Has anyone had any experience of this major annoyance which only seems to affect BT Internet not BT Connect. Obviously if anyone knows a fix my clients would be overjoyed!