Step Wise Manual Letterboxes mail settings for thunderbird
If you don't have a Letterboxes mail address. you can create an email id from here then you can Letterboxes 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, Letterboxes Email address and Password then press Continue.
Click on the Manual config menu at bottom.
Enter Below Letterboxes 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 Letterboxes 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 Letterboxes email account on your Thunderbird.