Please post your outgoing information from outgoing server (SMTP) in account settings.

The outgoing server is set "smpt.mail.yahoo.com" It is using port 587. For whatever reason, I cannot send out mail.

My provider is Comcast. However, they did away with their email and transferred it to Yahoo.com. I still use my original email address that I have always used with Thunderbird, edd.diamond@comcast.net I have contacted Yahoo. They told me that all of the settings in Thunderbird are correct. The same information works in outlook.

Any suggestions would be greatly appreciated.

Thank you, Edd Diamond

What is the authentication method being used for that SMTP server (oauth is required by yahoo)

As outlook does not even have separate usernames and authentication methods for incoming and outgoing accounts that might be were the issue lies.

Do you have an antivirtus that scans outgoing mail? Disable that function.