Answer: Delete the email account you have already set up, start again and follow these steps:

1. Tools -> Account Settings
2. Add Account -> New Account Setup -> Choose Email account
3. Identity:
   • Your Name: Firstname Lastname
   • Email address: name@domain.com
4. Server Information:
   • Choose IMAP
   • Incoming Server: mail.yourdomain.com
5. User Names:
   • name@yourdomain.com
6. Account Name:
   • name@yourdomain.com
7. Finish -> OKThunderbird might ask you for email account password, enter it.
8. Inside your Thunderbird right click on the email account -> choose Properties
9. Dialog box will open, go to Server Settings -> click on ‘Advanced’ button
10. Second dialog box will open, in IMAP server directory write: INBOX, click Ok on the second dialog box
11. On the first dialog box on the left below find -> Outgoing Server (SMTP), click on and choose ‘Add’
12. A dialog box will open with title ‘SMTP Server’ enter the following settings:Settings:
    • Description: name@domain.com
    • Server Name: mail.domain.com
    • Port 25

    Security and Authentication:

    • Check box ‘Use name and password’ should be checked.
    • Username: name@yourdomain.com

Confirm all dialog boxes with OK, close Thunderbird and reopen it again. You may be asked for your password again, place the password and check the box to save it.

This is the whole process of setting up an email account with Thunderbird.