A friend uses this email service and is having problems with one sender's attachments which are being apparently scanned by a Symantec product in the email system and a 'malformed container' being located, blocking the attachment and also slowing his machine to a crawl. He uses Avast as an AV programme.
I am not familiar with the BT Yahoo email system, and I see from Google that this problem is not uncommon. I have had no difficulty downloading/viewing/forwarding the problem emails or attachments he has forwarded to me and no AV warnings have been triggered, so I assume it is an over-zealous BTYahoo issue, just like the way it pops some of your friends emails into its spam box, doesn't tell you, and then deletes them (silently) after 30 days
Another friend was losing a significant number of 'genuine' emails that way.
Is there any way that he can 'turn off' this Symantec scanning and rely on Avast? Not being a 'customer' I cannot see his control panel.