Blocked & MSLN specific ports

This guide lists the ports currently blocked on the borders of the MSLN network, as well as the ports MSLN services designate for specific applications.


  1. Blocked Ports
  2. MSLN Port Designations

Blocked Ports

All of the following ports are blocked on the borders of the network due to abuse by bad actors and prolific viruses:

  • TCP/UDP 135-139 (Windows NBT)
  • TCP/UDP 445 (Windows SMB)
  • TCP/UDP 161-162 (SNMP) - Blocked throughout the network for non MSLN-owned equipment.
  • TCP 1433 (MS SQL Server)
  • UDP 1900 (Universal Plug and Play)

All other ports are open with the exception of port 25, which is only allowed for destinations with a 130.111.32.X ip address. This is to ensure that all outgoing mail-server messages are routed through See more information at the MSLN Email FAQ.

MSLN Port Designations


Our mail server accepts incoming SSL connections on 3 ports:

  • 25
  • 465
  • 587

Some ISP's do not allow outbound port 25 traffic. Verizon and are two ISPs that do not allow outbound port 25. In order to get around this, use one of the other two ports listed above. See our Email Client Configuration Guides for instructions.

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