''<p>Robert Slusser [[#question-1451681|said]]</p>'' <blockquote>When I mark a received email as Junk, how to block future emails from that address? </blockquote> I wrote a support article on exactly that about 10 years ago. https://support.mozilla.org/en-US/kb/blocking-sender Then we have this support article on how the junk filtering works. https://support.mozilla.org/en-US/kb/thunderbird-and-junk-spam-messages The take away from all of that discussion is Thunderbird has no regard to the sending address in junk filtering as it is irrelevant. The only time it is used at all is in the whitelisting of addresses in your various address books per your settings.