Thunderbird does not provide an option to block email from specific people or domain.
Fortunately, you can use message filters to automatically dispose unwanted messages.
1. On the sender's email that you wish to block, right-click on sender's address and choose Create Filter From...
2. The filter rules window will be automatically opened with the sender's email address.
3. Name the filter appropriately.
4. Change the action to perform to Delete Message.
5. Click OK to save the filter.
If the sender tries to send another email to your email address, the email will be automatically deleted.