On Mon, 26 Aug 2002, Jeroen Massar wrote:
ISP's should actually block port 25 outgoing, or even better, reroute/forward it to their own mail relay.
As a user, I pay my ISP to forward IP packets. If there happen to be TCP segments in those packets, that's something between me and the person the packet is addressed to, whether the destination port of those TCP segments is 25 or something else. As a network administrator, I don't want to filter applications. It burns too much CPU time on my routers, it costs me too much time to maintain those filters and it doesn't work anyway. Application people should make their applications secure and not impose restrictions on the network because they're too lazy to come up with a new protocol once every two decades or so.