Yes, it could also be that -- the ports aren't terribly unusual though. The matchmaker cycles between ports 80 and 8081 each version update. (I'm sure 80 isn't blocked as that's web default)
IP address is 40.121.22.148 or
matchmaker.magequit.comI'm curious what you get if you visit that address in your browser. I receive ERR_EMPTY_RESPONSE which is what the matchmaker is programmed to return when sent an unrecognized request (in this case a standard GET). I imagine your browser will not be able to resolve the address if it is indeed an issue with your ISP. If it is a DNS resolution issue, than you'd receive a different response for visiting the IP address vs the named address, but I doubt this is the case.
Who is your internet service provider if you don't mind me asking?
Hope this helps.
Brett