User Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36 Steps to reproduce: Delete unwanted mail that often gets through and be able to block and further mail from that source. Can do it on Gmail and Outlook. Would be very useful.
Please note: Bugzilla is NOT a support forum. It is a tracking system for bugs in Mozilla products. This is a support question. You can get support here: https://support.mozilla.org/en-US/products/thunderbird That said, for what you want to do, you define a filter: Tools > Message Filters. A filter action can be to move the message to a folder or delete it.