Oleg, they are apparently filtering based on content. We get no bounce from them at all, and they will not talk to us. So all we can do is guess.
2big, I appreciate your concern, but before you go off the deep end. If you wish to discuss those matters, then do so privately. Nothing you mentioned is really a problem for us. And if companies are building spam fillters based on PTR records, then they are in the wrong, not us.
Our name service is a bit screwy as AT&T insists on handling the reverse lookups and refuses to make us authoritative for the IP block.
The only problem is with MSN/Hotmail and Yahoo. They do not bounce thier emails when they decide not to deliver them. I have a real problem with that. If a service wishes to filter/block an email from delivery, they should bounce back with an error code indicating such. Giving us a satisfactory delivery code, but not delivering the email is just wrong.