before setup your Mozilla Thunderbird, pls make sure you have below information
incoming mail server : mail yourdomain.com
outgoing smtp server : smtp.yourdomain.com
email address : firstname.lastname@example.org
password : *****************
This tutorial will help you set up the Mozilla Thunderbird™ e-mail client to work with your e-mail account.
To Set Up Your E-mail Account in Mozilla Thunderbird
In Mozilla Thunderbird, from the Tools menu select Account Settings.
Select Email account, and then click Next.
Enter your name and e-mail address.
Select POP or IMAP as the type of incoming server you are using. Your incoming server is mail.yourdomain.com for POP, or imap.yourdomain.com for IMAP. Click Next.
Enter your e-mail address for the Incoming User Name, and Outgoing User Name. Click Next
Enter a name for your email account and click Next.
Verify your account information and click Finish.
In the Account Settings window, select Outgoing Server listed below your new account.
Type smtp.yourdomain.com for the Server Name and change the Port setting to 465.
Select Use name and password and enter your e-mail address. Thunderbird will ask you for your password the first time you try to send mail. Click OK.