outgoing mail

If incoming mail is working, I’d look at the outgoing SMTP settings first. Thunderbird uses a separate server for sending, and sometimes an update, password change or provider change can mess with that connection.

Go to Account Settings > Outgoing Server (SMTP) and check that the server name, port, security setting and username match what your email provider recommends. Also make sure the username is the full email address if your provider requires it. Don’t guess the settings, check the provider’s support page. Thunderbird Help

If you have more than one email account, make sure each account is linked to the correct SMTP server. I’d also check whether your antivirus, VPN or firewall is blocking outgoing mail. Before changing too much, post the exact error message and tell us who your email provider is. That’ll usually point straight at the problem.

Below is the email error message I receive when trying to send an email:

Sending of the message failed. The message could not be sent because connecting to Outgoing server (SMTP) smtp.mei.net failed. The server may be unavailable or is refusing SMTP connections. Please verify that your Outgoing server (SMTP) settings are correct and try