Security (* administrator only)

The options on this page allow you to enable spam filters, antivirus scan, black and white list, content scan and authentication in order to protect your system and Synology Mail Server users.

Spam

Enable the options below to manage and avoid receiving junk mail.

To enable SpamAssassin spam filter:

  1. Check the box Enable SpamAssassin filter engine to filter out spam based on content-matching rules.
  2. Enter a number of days in the Delete spam interval field to specify when spam messages will be deleted.
  3. Click the SpamAssassin Settings button to see more options.
  4. Click OK to save settings.

Note:

To enable DNS-based Blackhole List spam filter:

Enable DNS-based Blackhole List filter based on a list of IP addresses of computers or networks to filter out spam published through the Internet Domain Name Service.

  1. Tick Enable DNS-based Blackhole List filter.
  2. Click the DNSBL Servers button to manage the list of DNSBL servers.
  3. Click Create and specify the Server and Server type. Click OK.
  4. Click Edit to edit the DNSBL server.
  5. Click Delete to delete the DNSBL server.

To reduce spam mails:

  1. Click the Advanced Anti-Spam Settings button.
  2. Tick the boxes to reject emails that match the selected conditions.

Antivirus

Enable antivirus to scan all incoming and outgoing messages for viruses. If an infected message is detected, the system will delete the message and notify the sender.

Note:

Black and White List

The Black and White List feature allows you to reject, discard, or allow certain messages based on various criteria, such as the sender, domain, or the mail client IP address. For example, you can create a rule to always reject messages sent from a certain email address (e.g. "menelaus@argos.com"), a domain (e.g. "argos.com"), or mail clients from a certain IP address ("192.168.123.456").

To create black and white list rules:

  1. Click the Black and White List button.
  2. Click Create.
  3. Specify the criteria for the rule, for example:
  4. Choose what to do with messages that fit the criteria:
  5. Click OK to save the settings.

Rule Priority:

  1. Messages that match multiple types of rules are handled in the following order: IP address of mail client > Sender rules > Recipient rules.
    • For example, there are the following two rules:
      1. IP address of mail client: 192.168.48.15 --> Reject it
      2. 'From:' address contains: username@mail.com --> Accept it
      In this case, if a message is sent from "username@mail.com," but the IP address of the client that sent the message is "192.168.48.15," then the message will be rejected, because IP address of mail client rules have greater priority.
  2. Rules with matching content but different actions are handled in the following order: Reject it > Discard it > Accept it.

Note:

To set daily sending quota:

  1. Tick Enable daily sending quota.
  2. Enter a quota to limit the number of emails users are allowed to send daily. You can also enter 0 if you do not want to impose any quota limits.
  3. Click the Advanced Settings button if you want to set an individual daily quota for specific users.

To filter emails by attachment file types:

  1. Click the Attachment Filter button.
  2. Click Create to enter file types. Emails that contain attachments of the listed file types will be rejected.

Note:

Content Scan

You can allow the system to scan messages for potentially dangerous content.

To scan emails for dangerous content:

  1. Tick Enable dangerous content scan.
  2. Tick the desired boxes:
  3. Click OK to save settings.

Authentication

You can enable authentication mechanism to validate inbound emails and reduce spams.

To enable SPF verification:

  1. Tick Enable SPF verification to verify sender identity and detect forged sender addresses.
  2. Tick Reject SPF softfail if necessary. Emails whose verification result is softfail will be rejected.

To enable DKIM:

  1. Tick Enable DKIM to sign your outbound emails and to validate inbound emails and the senders' signatures.
  2. Enter a DKIM selector prefix of your own choice, and click the Generate Public Key button to generate a public key.
  3. Add and update the public key to your DNS records using a TXT record, so that other mail servers will be able to authenticate your DKIM signature. The TXT record should be added as follows:

To enable DMARC:

  1. Tick Enable DMARC to validate the senders' email domains.
  2. Update your DNS records using a TXT record, so that your outbound emails will be able to pass DMARC authentication of other mail servers. The TXT record should be added as follows: