I have a documentation system that needs to send user updates regularily to users that do not sit on the same network. The network that the documentation system resides is up until now a closed one. I have to allow only mail sent from the network. I have a Netgear Prosafe firewall FVS318. I have simply created a custom rule that blocks all outgoing ports except for port 25 and now 53. is this sufficient?
The ports are now changed as shown in the pictures below