I'm also getting the same error message when trying to send messages via Thunderbird (v10.0.2).
It was working fine yesterday using smtp.mail.yahoo.co.uk (Port 465, Security SSL/TLS).
Today it has started giving the error message.
I tried changing to mail.btinternet.com but still got the error message.
Sending via the BTYahoo Webmail interface works ok.
So, If I alter my Thunderbird Option to send simple text email, my message is accepted by mail.btinternet.com........
Since I haven't updated my machine, I have to assume that BT (or the cowboys), have made some system change that is causing these errors - is there someone monitoring who will take this up with the backroom boys???
I think it's a Yahoo thing, judging by what's going on in other forums.
They obviously changed something last night.
No change for me this morning, can still only send Plain Text email
It's 7h07 here, and still not working for me. Here's what I wrote on the other thread...
I also use Thunderbird. The problem arose for me early yesterday morniing and it persists this morning.
I stupidly wasted time working through alternative Yahoo SMTP servers, with ot without SSL, before realizing it was a BT/Yahoo issue. I have now temporarily (perhaps permanently) overcome it by using a non-BT/Yahoo SMTP server.
Here are my observations...
Webmail works fine, whether modern or classic.
Reverting to classic webmail doesn't fix the Thunderbird problem.
Thunderbird will send an empty message without problem.
Thunderbird will send plain text messages without problem.
Thunderbird will send rich text HTML messages from a BT account if you use a non-BT/Yahoo SMTP server
Judging by the Mozilla forums, the problem exists from New Zealand to the United States
Seems I spoke, or rather wrote, too soon. I can send new emails and reply to emails, but when I tried to forward one I got the abuse failure message.
Have you perhaps set your email client to permanently send plain text messages?
I still cannot send new emails, or reply to emails, (other than blank or plain text emails) via BT/Yahoo SMTP servers
Nope, I haven't changed anything on the laptop I am using. Tools/Account Settings/Composition & Addressing has the Compose messages in HTML format box ticked for the only account I've set up on this machine. Will check the position on the desktop on which I first encountered this problem shortly.
I changed desktop Thunderbird setting back to HTML, and it won't send, reply to or forward emails. Think I'll switch to plain text and leave it there until forums indicate that the problem has been solved.