Configure a Spam Filter in Plesk

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This article explains which settings you can configure in the SpamAssassin filter.

Plesk for Microsoft Windows

Enable server-wide SpamAssassin filters

If you enable this setting, the emails sent to the mailboxes hosted on the Plesk server are analyzed by the SpamAssassin filter.

Apply individual settings for spam filters

If you enable the Apply individual settings for spam filters option, users can set individual spam filter settings for their mailboxes.

The rating that must be assigned to a message to be considered spam

To identify spam messages, the SpamAssassin filter performs a series of tests on the content and subject line of each message. Each message then receives a score. The higher the score, the more likely it is to be a spam message.

By default, the filter sensitivity is set to classify all messages with 7 or more points as spam. If your users still receive spam, you can increase the sensitivity by setting a lower value such as 6. If the SpamAssassin filter marks valid messages as spam, you should reduce the sensitivity by setting a higher value.

Do not filter if message size exceeds specified size

The analysis of a large number of emails can lead to a greatly increased utilization of the server. To reduce the server load, you can specify the maximum size of the messages to be filtered.

Put the following text at the beginning of the subject of each message detected as spam

At the server level, you cannot set the server-wide SpamAssassin filter to automatically delete spam. Rather, for the server-wide policy, you can only specify that messages should be marked as spam. The SpamAssassin filter can automatically add a specific text to the beginning of the subject line of a message.

Trusted locales

By selecting trusted languages and language groups, you can define the language characteristics of emails that are always to be forwarded by the filter. All messages specified in the specified languages and character sets are not marked as spam.

Plesk for Linux

Enable server-wide SpamAssassin filters

If you enable this setting, the emails sent to the mailboxes hosted on the Plesk server are analyzed by the SpamAssassin filter.

Enable server-wide greylisting spam protection

Greylisting is a spam protection that stores the email address of the sender and the recipient in a database for each email message received by the server.
When a message arrives for the first time, the addresses of sender and recipient are not yet contained in the database. In this case, the server first rejects the message with an SMTP error code. If the email comes from a trusted sender and the sender's mail server is configured correctly, a new send attempt is started and the email is finally accepted. If the message comes from a spammer, the email is not resent.

Greylisting also takes into account the server-wide and per-user blacklists and whitelists of email senders. Emails from whitelist senders are trusted by the greylisting protection system and accepted without prior greylisting verification. E-mails from senders on the blacklist are always blocked.

Apply individual settings for spam filters

If you enable the Apply individual settings for spam filters option, users can set individual spam filter settings for their mailboxes.

Maximum number of worker spamd processes to run *

To limit the server load generated by the SpamAssassin filter, specify the maximum number of SpamAssassin processes in the Maximum number of running worker spamd processes field (1-5). It is recommended to use the default value.

The rating that must be assigned to a message to be considered spam

To identify spam messages, the SpamAssassin filter performs a series of tests on the content and subject line of each message. Each message then receives a score. The higher the score, the more likely it is to be a spam message.

By default, the filter sensitivity is set to classify all messages with 7 or more points as spam. If your users still receive spam, you can increase the sensitivity by setting a lower value such as 6. If the SpamAssassin filter marks valid messages as spam, you should reduce the sensitivity by setting a higher value.

Put the following text at the beginning of the subject of each message detected as spam

At the server level, you cannot set the server-wide SpamAssassin filter to automatically delete spam. Rather, for the server-wide policy, you can only specify that messages should be marked as spam. The SpamAssassin filter can automatically add a specific text to the beginning of the subject line of a message.