Junk Mail Filtering


Postbox features adaptive junk mail filtering to help you keep your Inbox free of unwanted messages. Initially, junk filtering may not work perfectly, but over time, Postbox will improve based on the training it receives. 

Configuring Junk Mail Filtering

When an account is added to Postbox, adaptive junk mail filtering is on by default. To configure your junk mail settings for a specific account, go to the following preferences/options window:

  • macOS: Postbox > Preferences > Accounts > [your account] > Junk Settings
  • Windows: Tools > Options > Accounts > [your account] > Junk Settings

You can enable/disable junk filtering for a specific account and decide where junk messages are moved after they arrive, how long they are saved, and what email addresses to trust. In addition, you will find the option to enhance junk filtering by enabling SpamAssassin or SpamPal.

Global Junk Mail Settings

Postbox offers global junk mail settings that will affect all accounts. Go to:

  • macOS: Postbox > Preferences > Security > Junk
  • Windows: Tools > Options > Security > Junk

Here, you can configure what happens when you mark messages as Junk (i.e. whether it is sent to the Junk folder or kept in the current location). 

Training Postbox's Junk Mail Filter

Postbox must be trained for junk processing to work correctly, including marking both types of messages as either "Junk" or "Not Junk." It's also recommended to mark various message types and sources – marking 500 messages from the same source is not as effective as marking 500 messages from different sources.

When Postbox is trained to filter Junk, its knowledge spans all configured accounts. Therefore, if you add a new account in the future, Postbox will start filtering Junk right away.

You can mark messages as Junk or Not Junk in the following ways:

  • Click the Junk/Not Junk button in the Toolbar (can be added or removed from the Toolbar).
  • Select the message(s) and go to Message > Mark > Junk or Message > Mark > Not Junk
  • Select the message(s) and use the J and Shift+J shortcuts (Junk and not Junk, respectively)
  • Right-click a message and choose Mark > As Junk or Mark > As Not Junk

Resetting the Junk Mail Filter

Finally, if you believe Postbox was trained incorrectly, you can click the Reset Training Data button for a fresh start. This setting can be found at:

  • macOS: Postbox > Preferences > Security > Junk
  • Windows: Tools > Options > Security > Junk

Disabling the Junk Filtering

To disable Junk settings, navigate to:

  • macOS: Postbox > Preferences > Accounts > [your account] > Junk Settings
  • Windows: Tools > Options > Accounts > [your account] > Junk Settings

Then disable the checkbox for Enable adaptive Junk mail controls for this account.


When a message is marked by Postbox as Junk, a circle icon with an exclamation mark will appear next to the message:

If there are messages in the Junk folder that do not have the yellow circle icon, then the junk filtering (and the subsequent move to the Junk folder) was accomplished on the server before Postbox had the chance to evaluate and tag the messages as Junk. Postbox's junk processing occurs as messages arrive in the Inbox, but if the server is moving the messages directly to the junk folder, this processing doesn't happen. However, you can still mark a message as Not Junk, so long as the message appears in the Junk folder.

If you mark a message as Junk, but instead of moving to the Junk folder the message returns to the Inbox, then you may not have the Junk function mapped to the correct folder. 

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