I wonder which ISPs are still doing so. I know comcast has been doing that but they cancelled it after many complaints. It seems to be the same case for Verizon.
You're mistaken. Comcast most certainly does port 25 filtering, although not necessarily on every line at every moment. So does Verizon, AT&T, and every other large North American consumer ISP I know. Look, kids, it's not 1998 any more. These days outgoing traffic to port 25 is approximately 99.9% botnet spam, 0.1% GWL, and 0% legitimate mail. Blame the botnet herders and the vendors of cruddy software that year after year still is full of trivial exploits. If you can make the botnets go away, I will be happy to lead the charge to unblock all those ports. If it's important to you to have an unfiltered connection, pay for business service that has a static IP, or arrange to tunnel to some host that does. R's, John