As far as I know, Telus has been blocking port 25 to servers other than it’s own mail servers for about a month now. Possibly longer, but that was the first time I’d heard of it. On the Shaw side, I had been fine and things were peachy until this morning when my outgoing mail started bouncing back.

Shaw had finally joined in…

A friend of mine tells me that Shaw had actually been implementing this one area at a time over the past year, so Telus could have been doing the same as well. Port 25 blocking isn’t something that’s just recently popped up though. A number of providers in the US have already been doing this for a while now and we’re only now essentially “catching up” here in Canada.

The reasoning to this port 25 blocking? “To reduce the volume of Unsolicited Bulk Email (SPAM).”

While this sounds great and all, I wonder how well this actually works. I don’t know when the US started doing this, but I’d really like to know if there has been any substantial drop in SPAM since implementing this block. Sure it prevents zombies from spewing out massive amounts of junk mail and I’m sure in the end there’s some drop in bandwidth usage but maybe that’s the real goal here. To save on bandwidth costs.