I have a love-hate relationship with Telmex. They are a monopoly which I hate, and their services is expensive. But their service  have some redeeming qualities: they give you a real ip adress, they don't filter the content, and they don't block any port; at least they didn't. That have recently changed when they decided to outgoing calls to port 25 just after christmas. They decided to do that because they had been transform in one of the biggest spamming source in the world (to reactive your port 25 access click on this link). I think they decided to do this silently so that only people who are technically saavy would discovered it. However, it did took me a couple of hours figuring why I couldn't send emails and finding the link to correct the issue. Anyway, after this was done, my college which prides itself  of their technology decided that the best thing to do to overcome this issue is giving everyone the link to open their port 25. They should have opened a new port, which is the standard way most smtp servers are working right now instead of giving you the pliers to break your own lock.