I too had a phone call yesterday evening (4/12) and told problem thought to be fixed - Have just tested and it isn't. Thanks for your post liquorice - at least when I speak to them today I'll know it isn't just me who isn't fixed !
Yes, still having problems although to be fair there has been a slight improvement. I have escalated this to BTs Board and they do seem to be making efforts to solve this problem. I am now getting updates directly from the Director Of Online's Team. I am told that our mail accounts have been migrated to other servers and this has improved or even fixed the issue for many. However some of us are still suffering. As you say BT seem to think that bandwidth may be a contributory factor. I am awaiting the next update. Like you, even with my slow broadband I never used to have this problem until March this year which seems to have coincided with the all new Yahoo mail. Will keep you posted as to progress or otherwise.
Likewise, thanks for the offer but the (my) issue now sits with Alison Slee on behalf of Nick Wong's team at BT.
This problem still continues, I have another client reporting the error again, as soon as she gets an email with an attachment over 3MB the server terminates the connection, when are BT going to admit they have a problem