Thunderbird and Junk / Spam Messages
To deal with the large amount of unsolicited email ("spam" or "junk mail") that most people have to cope with, Thunderbird uses an adaptive filter that learns from your actions which messages are legitimate and which are junk.
Training the junk filter and Tell Thunderbird what is junk
In order for this filter to be effective, you must train it to recognize the messages that you consider to be Junk. To train the filter, simply mark messages as Junk. You can mark messages as junk in the message list by clicking in the "Junk" column in the message list:
Or you can also mark messages as Junk in the message pane by clicking the Junk button on the message header:
As you mark messages, Thunderbird learns the characteristics of your junk mail and can start automatically classifying messages. Once the email is marked as junk, it will automatically move to your Junk folder and from there you can delete the junk message.
Tell Thunderbird what is NOT junk
Because Thunderbird learns based on what is marked as junk, it's very important that you mark any email incorrectly labelled as junk or as "not junk". Otherwise Thunderbird will consider to mark emails like that as junk in the future. This will be especially important when Thunderbird is just starting to learn, but will improve the more you train it. At first check your Junk folder regularly. As time goes by, this can be done less frequently.
How To Unjunk Email
Just go into the “Junk” folder and click the “Not Junk Button” or the “flame icon” in the email incorrectly marked as junk
For Windows users: Take note when opening junk mail, please do not open the attachment (zip, or exe, or any file) it may contains virus and instantly harmed your computer.