Armstrong is committed to providing a secure internet experience. To protect its network and customers, it blocks certain ports. Ports 25, 67, 135-142, 161-162, 445, and 520 are blocked. Blocking these ports reduces network congestion and protects customers against common viruses and worms, malicious intruders, and other security exploits. Email hosting is limited to commercial customers subscribing to Zoom Professional or above upon request.