Email Message cancelled by system filter: The mail server detected your message as spam and has prevented delivery

Symptoms

SpamAssassin marks an email as spam, but doesn't deliver it to the spam folder, and a message similar to the following can be found in the Exim log.

2024-01-04 14:01:25 1rLUq7-0008RT-2a cancelled by system filter: The mail server detected your message as spam and has prevented delivery (50).

Description

Spam Assassin has a setting that will return a message to the sender instead of allowing it to be delivered if the spam score is too high. This setting should be set higher than the spam threshold or disabled if you want spam emails delivered to the spam folder.

Workaround

1. Log into WHM as the ‘root’ user.
2. Navigate to "Home / Service Configuration /Exim Configuration Manager."
3. Click the "Basic Editor" tab.
4. Click the "Filters" tab.
5. Increase the "Apache SpamAssassin™: bounce spam score threshold" value or disable this option.
6. Click the "Save" button.

Additional resources

Exim Configuration Manager