Thunderbird has its own Junk folder and doesn't use the Spam folder, nor the word "Spam". The Spam folder is put there by your email provider (Googlemail, in this case) and they populate it for you. Therefore, Google are doing this for you. Irritating, isn't it? Supposedly, if you move the message to the Inbox, or go to the googlemail webmail site and mark it as "not spam" then it should learn that you want these messages. In my experience, a large number of googlemail users mark anything they don't want as "spam", and this colours the way that their spam filters work. So IMHO it's rather futile trying to retrain googlemail's spam filters. To my mind, email comes in three flavours: 1) Useful stuff 2) Not useful but harmless stuff (commercial circulars, newsletters etc) 3) Bad Stuff™ that wants to steal your money or ID, or own your computer (3) is spam and should be eliminated. (2) is a nuisance but a necessary evil. If you want to use a service, you generally have to sign up and will therefore get a never-ending stream of messages pushing new services or offers. If these really annoy you, just unsubscribe. Don't report them as "spam", because they are not truly Bad Stuff™ (type 3). You're suffering from the likelihood that your correspondent has been reported as a spammer. In truth messages from their domain probably just annoyed a few too many email users. You may find that it's better to disable Googlemail's spam detector and use the Junk Controls within Thunderbird. At least you'll be training it on what YOU want and don't want, rather than being subject to googlemail's opinion. It may help to add this correspondent's email address(es) to your googlemail address book, via the gmail website, thereby whitelisting this sender. The sender's address may be in your Thunderbird address book, but gmail can't see this; you need to add the address to gmail's own address book.