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Configure mail size filtering settings

  • Published on Sep 2, 2026
  • 2 minute(s) read
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Mail size filtering settings in a policy detect emails based on their size, number of attachments, and attachment size.

Make sure that on the On-Access Settings page, the Scan Inbound Mails and Scan Outbound Mails options are selected.

You can configure mail size filtering settings for On-Access policy separately. Configure the On-Access settings for outbound emails. For example:

  • To block all outbound emails that contain more than three attachments, configure the Mail Size Filtering settings from On-Access policy.

Note

Mail size filtering for on-access scanning is not applicable for mailbox server role.

  1. From Policy Manager, select a submenu item that has the anti-virus scanner.

    The policy page for the submenu item appears.

  2. Select the policy as required from On-Access.

  3. Click Primary policy or any subpolicy you want to configure, then click List All Scanners tab.

  4. Click Mail Size Filtering.

  5. In Activation, select Enable to activate the email size filter settings for the selected submenu item.

    Note

    If you add a new filter to the policy, you can specify a time slot when to enable the filter, using What time would you like this to apply drop-down list.

  6. In Options, you can use:

    • Default Settings — To view a summary of the mail size option set that is used by default.

    • <create new set of options> — To configure mail size filtering options. The options are:

      • Instance name — Type a unique name for the mail size filter setting instance. This field is mandatory.

      • Maximum overall mail size (KB) — Specify the maximum size (in kilobytes) that an email message can be. You can specify a value from 2 KB to 2 GB, where the default value is 20,000 KB.

      • Maximum attachment size (KB) — Specify the maximum size (in kilobytes) that the attachments of an email message can be. You can specify a value from 1 KB to 2 GB, where the default value is 4096 KB.

      • Maximum number of attachments — Specify the maximum number of attachments an email message can have. You can specify up to 999, where the default value is 25.

    • Edit — To edit the selected option set.

  7. In Actions, click Edit. Specify the mail size filter actions to take, if the value exceeds the specified settings for these options:

    • Message Size

    • Attachment Size

    • Attachment Count

  8. Click Save to return to the policy page.

    Note

    Internal emails are not detected by mail size filtering rules.

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