If you search for the string "the connection to the outgoing server SMTP timed out" in the top right search field, there will be numerous articles with information about how to resolve this issue.

The most common solution is that Anti-Virus software needs to be switched off from scanning emails.

If the solutions offered don't work, please reply to the post and it will be relisted as in need of a solution.

Thank you for your solution - it worked. However, how do I now have my Emails scanned for viruses, please? Can you please tell me how this problem has come about - it never used to happen?

All things are in a constant change - TB is more visible but anti-virus software, operating systems, hardware and their drivers (to name a few) are constantly being updated.

Someone else will have to instruct you about emails and protection. I use Windows built-in Security Suite and it doesn't have a problem with the two email programs I've used.

I would start a new thread and ask the next question. That way, the question looks like it has no replies and someone may dive in.

Thank you for your solution - it worked. However, how do I now have my Emails scanned for viruses, please? Can you please tell me how this problem has come about - it never used to happen?

Disabling the mail scanner doesn't mean the real-time background scan is disabled - it will still respond to any infected attachments that are opened. Plus, you can always export or save a suspicious message and scan it manually.

http://kb.mozillazine.org/Antivirus_software

https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues

Aah, the failure to send Emails has re-occured so I doubt that it was Norton causing the problem. So I will reinstate the Email checking and I will sign off my problem.