I have 4 computers all running Thunderbird 60.4.0 (32 bit). I have two Email accounts. One is a @btinternet.com account. The other is hosted by 123-reg.co.uk. All 4 computers send and receive Email to the bt account. Three of them will not send Emails using the 123-reg.co.uk server. The fourth one works fine on everything. All receive Emails from the 123-reg.co.uk server. Initially when Send is clicked the message "Connected to smpt.123-reg.co.uk" is shown After a delay of around 30 seconds the following appears;- "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smpt.123-reg.co.uk timed out. Try again." The computer which does work is a Windows 7 Pro 32 bit machine. Those that don't send are all 64 bit machines. Two run Win 7 Pro and the third runs Win 10 Home. Comparing the settings on all 4 machines, they appear to be the same - so I don't know what the problem is. There are various articles relating to this problem on the web but they all relate to earlier versions on Thunderbird and the locations for changing "time out" settings remain a mystery. I'm not even sure that it is as simple as changing a "time out" setting. Any help would be much appreciated. PJW