1. Open your Mozilla Thunderbird
2. Go to Tools > Account Settings.
3. Click "Create a new account"
   
4. Choose "Skip this an use my existing email"
5. Enter Your Name, full Email Address and password , click "Continue".
   
6. At Mail account setup configure screen,choose Manual config .
   
7. Select the type of incoming server : IMAP.
   Enter the name of your incoming and outgoing mail server: mail. (enter your domain name) with Port number 143.
   
8. Click on "Re-test" the configuration and Click "Done".
9. Back to your Thunderbird main menu and go to Outgoing Server as below and confirm your Outgoing SMTP server.
   
10. Check the "Use name and password" box and assign your email account to the User Name and select "No" for Use secure connection.
    
11. You may start using Thunderbird by clicking on the top left "Get Mail" button.