yah, I too fail to see the relation between your problem and the reply they gave you.
This clearly does not fall under their support and they could just have said so. Why they mumbled something about not being responsible because you run your own nameservers... beats the hell out of me.
My best bet is they did a lousy job at reading your support ticket. They saw the words MAIL and PROBLEM looked at your DNS and said: "whoa, not our fault his mail does not get delivered. He is using his own DNS".
Ensim is a resource hog in my experience.
I get 100 max accounts per server on the same spec boxes i can easily get 200 with Cpanel so the move will not really cost much to do and it will simplify our admin.
Formerly: Managing Director, Hostroute.com Ltd & Marketing Director, Ultraspeed UK Ltd View my Professional Profile:www.gordonhudson.com
If your domain name was using the rackshack dns servers they could have checked the mx records to make sure they were set up ok. This is probably the only thing they would have done as well as thats the only support they have to offer. As you wern't using the rackshack dns they could not trouble shoot the problem from their end.
Maybe a little better explaination could have been provided in the email they sent you but basically what they said is true and valid.
Rackshack provides software support only insofar as it pertains to external services they offer. If your sendmail problem was due to a foulup with their DNS, they would fix that. I don't understand why people keep expecting Rackshack to provide software support, when you're getting a very cheap box because they don't provide software support.
I've had this problem before. I had a site having aliases point at other aliases to other aliases. The mail que had 1000s and 1000s of messages waiting to be sent out. I had to delete everything in the folder and kill the aliases. It was on a Ensim server.