Make sure you have subscribed to see the imap server spam folder. * Right click on imap mail account name in Folder Pane and select 'Subscribe' * select the 'Spam' folder and click on 'Subscribe' button * click on OK Now select to use that folder in your Junk Controls. * Right click on imap mail account name in Folder Pane and select 'Settings' * select 'Junk Settings' * select 'Enable adaptive junk mail controls for this account' * Select any address books you want to be used as a whitelist. * Select 'Trust junk mail headers set by 'Spamassassin' * select 'Move new junk messages to:' * select 'Other' and select 'Spam folder on imap mail account name' * click on 'OK' Additional Info links: * https://support.mozilla.org/en-US/kb/thunderbird-and-junk-spam-messages * http://kb.mozillazine.org/Junk_Mail_Controls