Thunderbird fails to sync junk folder unless user clicks on junk folder specifically. How can user sync junk folder automatically, since otherwise there is a chance false positives might go unnoticed?

Thunderbird is latest version 52.2.1 (32 bit) on Windows 10, all folders are subscribed, tried pressing "Get All New Messages" several times, restarted Thunderbird, tried disabling/enabling adaptive junk filter option. Server used is Dovecot IMAP with SUBSCRIBE turned on for the Junk folder. Issue does not happen in other clients whereupon receiving junk message the junk folder shows unread message flag.

3 Answers 3


It appears Thunderbird does not automatically sync junk or trash folders by default (tested latest stable and beta versions on Windows 10). The solution was to include junk folder in message synchronization settings (offline use settings).

Tools > Account settings > Synchronization and storage > Advanced > Select junk folder.

Updated for Thunderbird version 102

Right click Junk folder > Properties > Check the option When getting new messages for this account, always check this folder > Press OK

  • When I go to Account settings > Synchronization and storage > Advanced, it does not show me the junk folder. However, if I login into "the official web app" (Outlook) there is a junk folder.
    – user171780
    Aug 17, 2023 at 19:40

In my case what worked was right click in the account, then "subscribe", and here you select whatever folder you want.

  • Subscribing to a folder lets the client know to display it in the folder list tree, but it may not be checking for new mails in that folder automatically. See the update to my original answer. Aug 18, 2023 at 20:05
  • Indeed, after a few days I realized Thundrebird was not automatically checking those folders, they simply were there for me to check them. If is kind of a combined approach to make it work. Thanks!
    – user171780
    Aug 19, 2023 at 8:09

This method worked for me:

  1. Right click on "Junk" folder
  2. Click "Properties"
  3. Check mark "When getting new messages for this account, always check this folder"
  4. Click "OK"

This may be different in your Thunderbird version.

Edit: I found there is an answer which already has this method, but I was unable to see this method in that answer when I was finding the solution, so I am keeping my answer so that others (like me) can see easily.

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