Check for the site address of your SMTP mail server. 'Tools - Account Options' In the left pane, search for 'Outgoing Server (SMTP) You may have to scroll to the bottom of that left window. In the right-hand window, search for your provider (probably marked as default), remember the 'server name' and verify your username. Close the screen.

Now check the password for that log-in 'Tools - Options - Security' press 'Saved passwords' On next screen search for your mail providers server name or just search for smtp You can then press the 'Show password' button. You will have to confirm 'Are you sure..?' Thunderbird should be showing the password that it is trying to use to gain access when sending mail.

Are you using the same email provider for BOTH incoming and outgoing messages, even with two different log-ins?

If you use different providers, some SMTP servers will not allow you to send an outgoing message until you 'poll' for new messages first. This to prevent spammers from taking advantage.

Links to other related problems https://support.mozilla.org/en-US/questions/1023036 https://support.mozilla.org/en-US/questions/1001288

TB-38.3 Win10-PC

Thank you - that was very helpful, and my passwords are correct.

I use different providers because we have to use a satellite company for our broadband, PCQ, which provides our smtp connection, but I use my webhosting company for incoming emails, www.trailrides-wales.com.

This arrangement has worked OK for about three years, but two weeks ago, Thunderbird stopped sending. The error message is that "pcq.net have timed out".

changed a modem perhaps, or installed a new gateway or wifi box?

Does your anti virus have a firewall? Is Thunderbird explicitly allowed access on the ports set in the outgoing server settings