Using Thunderbird I often find my outgoing emails to smtp talktalk server are blocked on ordinary mode and safemode and deleting password from password manager doesn't solve issue. Emails are fine from tablet and webmail so its not a talktalk issue. It happens whether or not there are attachments. Only solution I've found is to change my talktalk password but that is a pain as I'd have to do it almost very week. imap outgoing to gmail is not affected. Version is most recent. Error message is "ending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.talktalk.net was lost in the middle of the transaction. "