1) Open Thunderbird.
2) Click the 'Tools' menu, and select 'Accounts.'
3) Click 'Add Account'.
4) Enter your name as you would like it to appear in the 'From' field for all outgoing messages. Also supply the password for this email account and click 'Continue'.
Select 'Email Account' and then click 'Next.'
5) Thunderbird will attempt to automatically detect and finalize the configuration for your incoming and outgoing server settings. Please allow the automatic configuration utility to finish.
6) Once finished click 'Edit'.
7) Change the username to the full email address for which the email is being setup.
8) You may set the Incoming protocol to either POP or IMAP. The default ports are - 143 for IMAP and 110 for POP3. You may select 'STARTTLS' from the drop-down menu as connection security.
9) In the case of Outgoing server key in "mail.yourdomainname.com". You may select STARTTLS from the drop-down menu. The default 'SMTP' port is 25.
10) Click on Re-test Configuration to verify whether the configurations are correctly setup.