Have you checked your anti virus is not scanning email and secure connections? Both things cause issues, especially after an update to Thunderbird.

I am getting the same error. "Sending of the message Failed. Failed due to unexpected error 80004005. No description is available. The message could not be send using outgoing server (SMTP) smtp.gmail.com for an unkown reason. Please verify that your outgoing server (SMTP) setting are correct and try again. "

This email address is on multiple computers in the same office and it is working for everyone else. This user has had it working without issue for at least 6 month and today it just stopped working. The user has multiple gmail accounts setup in his thunderbird with the same SMTP and port and they are working fine just this one account.

User is on windows 10 pro x64

I've tried the following: 1. Deleted the account and added it back 2. Made sure Thunderbird is up to date. 3. Made sure all windows firewalls are disabled 4. disabled antivirus (Paid AVG version) 5. Started thunderbird in safe mode

Anyone know what can be causing this issue and anything else that I can try?

Since this is a IMAP account, you should be using OAuth2 authentication for both the incoming server and the outgoing smtp. Plus, your TB should be 60.9.1 or 68.3.1, and cookies for *.google.com must be enabled in Tools/Options/Privacy.

http://kb.mozillazine.org/Using_Gmail_with_Thunderbird_and_Mozilla_Suite

1. TB version is 68.3.1. 2. Cookies are enabled. 3. OAuth2 authentication is set. Still getting the same error anything else you can recommend?

I tested moving the outgoing authentication to Normal password and I was able to send out an email but got an error when it tried to save it to the sent folder.

I don't know why it fails to work with OAuth2 authentication, but the error on saving to sent might be fixed by unchecking 'Place a copy in...' in the Copies & Folders section in Account Settings. Gmail accounts automatically copy sent messages to Sent.

I don't want to send out emails using "Normal Password" all other users have the authentication method set to OAuth2, it must be something specific to this pc since it was working fine for months and then suddenly stopped working just a couple days ago. Any other suggestions would be greatly appreciated.

Try running Windows in safe mode with networking and see if it makes any difference. Different computers with the same account that's working may have different startup apps, especially security/AV, that affect the connection between TB and gmail.

Normal password authentication, with a strong password, is not less secure than OAuth2 authentication.

I ended up just going with Normal Password. Thank you very much for your help. Happy New Years!