Incoming spam messages are delivered to mailbox in Plesk

Symptoms

The following Plesk Anti-spam tools are used, however, incoming spam messages are still delivered:

• SpamAssassin Spam Filter
• DKIM, SPF, and DMARC Protection
• DNS Blackhole Lists
• Plesk Premium Antivirus
• Server-wide Blacklist
• Greylisting

Cause

The spam filter is not optimized.

Resolution

The following measures can be applied for spam filter optimization:

1. Decrease spam filter sensitivity:

   For the particular mailbox

   Note: it is possible to edit spam filter sensitivity for the particular mailbox if only the Apply individual settings to spam filtering checkbox is enabled at the Plesk > Tools & Settings > Spam Filter page.

   1. Log into Plesk.

   2. Go to Plesk > Domains > example.com > Email Addresses > johndoe@example.com > Spam Filter.

   3. Click the Show Advanced Settings link.

   4. Decrease the Spam filter sensitivity and press the OK button to apply changes.

   Server-wide

   1. Log into Plesk.

   2. Go to Plesk > Tools & Settings > Spam Filter page.

   3. Decrease the Spam filter sensitivity and press the OK button to apply changes.

2. Train SpamAssassin according to the article:

   How to train SpamAssassin?

3. Consider to use additional anti-spam tools.

   • Warden Anti-spam and Virus

   • SpamExperts Email Security

4. Lock spammer mailboxes by applying solution from the following article: How to block a particular mailbox or a range of mailboxes belonged to a specific domain from sending emails to Plesk server?