Step Wise Manual Optonline mail settings for thunderbird
If you don't have a Optonline mail address. you can create an email id from here then you can Optonline 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, Optonline Email address and Password then press Continue.
Click on the Manual config menu at bottom.
Enter Below Optonline incoming server settings.
In incoming click on the dropdown menu and select IMAP.
Add server host :mail.optonline.net
Port: 993
select SSL/TLS
Enter Below Optonline outgoing server settings.
In outgoing select SMTP.
Add server host :mail.optonline.net
Port: 465
select SSL/TLS
Tap on Done. Now you are ready to use your Optonline email account on your Thunderbird.