Security

You can enable spam filters, antivirus scan, black and white list, content scan, and authentication to protect the mail system and client users.

Spam

Enable spam filters and set security rules to avoid spam.

To enable SpamAssassin filter:

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

Note:

To enable DNS-based Blackhole List filter:

Use DNS-based Blackhole Lists (DNSBLs) to filter out spam published through the Internet Domain Name Service.

  1. Tick Enable DNS-based Blackhole List filter.
  2. Click DNSBL Servers to manage the server list.
  3. Click Create and specify the DNSBL Servers and the Server type. Click OK.

To apply advanced security rules:

The high-security settings here might block legitimate messages, so please make sure you fully understand which type of senders you want to block before enabling any options.

  1. Click Advanced Anti-Spam Settings.
  2. Enable the following options based on your needs:
  3. Click OK to save the settings.

Antivirus

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

Note:

Black and White List

Use the black and white list to reject, discard, or allow certain messages based on various criteria, such as senders, domains, or client IP addresses. For example, you can create a rule to reject messages sent from a certain email address (e.g., "menelaus@argos.com"), a domain (e.g., "argos.com"), or clients from a certain IP address ("192.168.123.456").

To create black and white list rules:

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

Rule Priority:

Note:

To set daily sending quota:

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

To filter messages by attachment file types:

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

Note:

Content Scan

Allow the system to scan messages for potentially dangerous content.

To scan messages for dangerous content:

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

Authentication

Enable authentication mechanism to validate inbound messages and reduce spam.

To enable SPF:

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

To enable DKIM:

  1. Tick Enable DKIM to sign outbound messages and to validate inbound messages based on sender signatures.
  2. Enter a DKIM selector prefix of your own choice and click Generate 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 senders' email domains.
  2. Update your DNS records using a TXT record, so that your outbound messages will be able to pass DMARC authentication of other mail servers. The TXT record should be added as follows: