said by droobie:
Many things could be claimed in network management, like ISPs that block access to DNS servers outside of their network. Doesn't make it right or 'neutral' however. There's plenty of perfectly valid mail going over port 25 and not all DNS traffic is a DDOS attempt.
See my above post regarding SMTP blocking.
For DNS blocking, there are very valid reasons for doing that too. The main reason being that it blocks rogue dns servers harming their customers.
As you point out, there are legit purposes, but it is a balancing act between protecting customers from harmful stuff, and leaving things open.
Enabling or disabling blocks at the account level would be nice for those who do want to use a 3rd party DNS service, but it does add an additional cost to implement.