This is pretty standard and a fairly responsible thing for them to do, but unblocking for individual customers should be possible. Use SSL/TLS, which is on port 465. Or I guess change ISPs.

What email server are you trying to use?

Spark's Port 25 filtering works both ways.  Inbound and outbound port 25 is blocked.

I'm personally surprised anyone in this day and age needs port 25 unblocked.

You should be talking to your mail server over SSL so 465 or 587 would be the ports you use to connect so having port 25 blocked wouldn't impact you at all.

Having inbound port 25 means you are leaving yourself open as a spam relay. That's just bad (TM).