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Block IP addresses manually

  • Published on Sep 2, 2026
  • 1 minute(s) read
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You can block a specific IP address or a range of IP addresses from sending emails to your organization irrespective of their IP address reputation. To enable this option, you must update the following registry.

Blocking IP addresses manually can be used only on Exchange roles, Edge, and MailBox.

  1. On the system where TSME is installed, navigate to this registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\McAfee\MSME\SystemState

  2. Add the String value IPBlackList.

  3. Assign the IPv4 address that you want to block from sending emails.

    You can block multiple IP addresses using a semicolon. You can also block a range of IP addresses using the wildcard *. For example:

    • 10.21.22.* — Blocks all IP addresses from 10.21.22.0 to 10.21.22.255

    • 10.21.*.* — Blocks all IP addresses from10.21.0.1 to 10.21.255.255.

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