Open up thunderbird and head to the right hand menu area which contains your email addresses, and right click on top of your Computerisms hosted Email Account
In the context menu that appears, select Settings
Head down to the bottom of the side menu, to the option labeled Outgoing Server (SMTP)
Find the item in the list named yourdomain.tld Mail - mail.yourdomain.tld and select it
Check the details of the selected server below:
If it says Port: 465 and Connection Security: SSL/TLS then congrats! You're already set up! You can skip the rest of this guide
If you instead see Port: 587 and Connection Security: STARTTLS we'll need to make some changes, following the steps below
Click on Edit... on the right hand side
Change the Port under the Settings header to 465 and the Connection Security down under Security and Authentication to SSL/TLS and click on OK.
You're done! Feel free to close the account settings tab that had been opened in the main Thunderbird window
