Please explain more about your computer and what you think or know is occuring. What OS are you using? What version of Thunderbird are you using? Are you talking about a Pop or Imap account? What process are you using? Are you attempting to manually mark as junk by: # selecting email to read and then clicking on the 'Junk' button? # using right click on email in list > Mark > As Junk? # Enabling the Spam column header and clicking on the relevant junk icon? Are you attempting to use a Message Filter to auto mark mail incoming to Inbox as junk? If yes, then post an image of the filter Have you set up the Junk Control settings for the account? Please post an image of Junk Settings for the account. If you have an imap account - what is the name of your 'junk' folder eg: is it called 'Spam'. Logon to webmail account via a browser - how many folders are called 'Spam' or 'Junk' or similar? I need to know if you really are putting emails into the correct default server folder for 'Spam/Junk'. When you attempt to mark as junk what is occurring? examples: Does email go to junk/spam folder but then reappears back in Inbox ? Nothing happens ? Is the sender including your name in the From email address as the Display name?