It's pretty common to have outbound traffic to port 25 blocked as an anti-spambot measure. Sometimes you can call them and get them to remove the block, other times it's non-negotiable.
Most cloud servers do this too. Spam has basically destroyed smtp as an open federated protocol anyway. Network reachability is the least of the issues you'll face trying to run your own mail.
Lesson: any distributed or federated protocol that is not robust against abuse is doomed.
Lesson: any distributed or federated protocol that is not robust against abuse is doomed.