You can't stop people sending to you. But you can train Thunderbird to recognize what you don't like. Mark them as Junk. Mark non-Junk messages as Not Junk. It's not immediate, but over time Thunderbird will start detecting such messages and will mark them as Junk automatically. https://support.mozilla.org/en-US/kb/thunderbird-and-junk-spam-messages But seriously, 25 a day is "too many"? I'd be grateful if my Junk was at such a low level. Indeed, at only 25 a day it will take some time for the training to take effect. It needs hundreds of messages to become really useful.