Step Wise Manual Fastemail mail settings for thunderbird
If you don't have a Fastemail mail address. you can create an email id from here then you can Fastemail email login.
Open Thunderbird Software App. Click on Email
When you click on the email, pop-up Set UP an Existing Account Screen.
Enter Your name, Fastemail Email address and Password then press Continue.
Click on the Manual config menu at bottom.
Enter Below Fastemail incoming server settings.
In incoming click on the dropdown menu and select IMAP.
Add server host :mail.messagingengine.com
Port: 993
select SSL/TLS
Enter Below Fastemail outgoing server settings.
In outgoing select SMTP.
Add server host :mail.messagingengine.com
Port: 587
select SSL/TLS
Tap on Done. Now you are ready to use your Fastemail email account on your Thunderbird.