Start by checking the following: There's more than one place to set up and deal with 'Scam' and 'Spam or Junk' and you would need to check all of them.

• Settings > Privacy & Security
• Scroll to 'Security' section
• Select the check box 'Tell me if the message I'm reading is a supected email scam'

There is a also default setting for Junk:

• Settings > Privacy & Security
• Scroll to 'Junk' section

This basically just sets up what to do with a junk mail and whether to auto enable adaptive junk logging. It does not set up individual accounts in this location.

Advise you use:

• Select 'When messages are marked as junk'
• Select 'Move hem to the accounts Junk folder'
• Select 'Enable adaptive junk filter logging'

Please note that the adaptive junk filter 'logging' does not mean adaptive junk filtering is enabled. This is just enabling the logging.

Junk Settings for individual accounts need to be set up so that the default knows what account uses what folder for 'junk'. You also need to enable adaptive junk on an account.

• In 'Account Settings'
• Select 'Junk Settings' for account

Advise you set up as follows:

• Select 'Enable adaptive junk mail controls for this account'
• Select checkbox for any address book that you want to use as a whiltelist - basically contacts are good.

Advise do not Select ' Trust junk mail headers set by X' unless you really want to because if server spam filters say it's junk then Thunderbird will follow your rule and also mark as junk.

Destination and Retention

• Select 'Move new junk messages to'

Not sure if you have pop or imap so.... IF POP account:

• Select: 'Junk folder on' and name of pop account.

IF IMAP account:

• Select 'Other' and choose the correct name of server folder eg: 'Spam on imap account'

Please note - many servers will auto empty the Junk/Spam folder periodically. Some do it once a week, others once a month. You might want to set up your own to delete junk older than x, but since good mail could end up in junk/spam, personally I would advise you do not select that option and instead empty the Junk manually via a right click on Junk folder and selct 'Empty Junk' after you have checked it. Then please remember to Right click on Junk and select 'compact' to remove all traces of old emails.

The adaptive junk filter also needs to be trained, so it learns what you say is junk and also what you say is 'not junk'. This filter learns reasonably quickly but it depends upon whether you initially tell it what is what.

Additional help in Help Article:

• https://support.mozilla.org/en-US/kb/thunderbird-and-junk-spam-messages

Emails in Junk/Spam folder or indeed any folder eg: Inbox I would suggest you enable the column header called 'Spam' This displays a 'flame' icon next to each spam/junk email. If the flame icon is greyed out then server set it as spam and put it into the server spam folder which imap accounts can see. If flame icon is red/orange then Thunderbird marked it as spam/junk.

So are you using Pop or Imap accounts? Have you checked all the settings to ensure you are using everything correctly? Is the 'flame' icon in 'Spam/Junk' red or greyed ? Is the 'flame' icon for junk mail in Inbox red or greyed ?

I changed the folder to "other" in the account settings and it appears to be working correctly again. Thank you, lots of good information in your response.