You can mark it as ''Junk'' in Thunderbird, but that's part of a training process and won't immediately have any effect. Thunderbird has no concept of "Spam" as such. If it has specific and persistent characteristics, then you could set up a Message Filter to deal with it. https://support.mozilla.org/en-US/kb/organize-your-messages-using-filters Personally, I get a fair amount of UCE/Spam/Junk but little of it is sufficiently consistent as to be trivial to filter. Spammers work to avoid being easy to identify and a simple filter will rapidly be made obsolete as the spammers tweak their content. They rarely use the same "From:" address for any great period of time, and only a numpty would keep using a recognizable word such as "viagra" or "cialis"; these words are usually disguised in such a way as to require fairly sophisticated filtering to spot them. If you are truly getting annoyances from one specific address then I doubt it is strictly what we would call "spam".