Server DNS ignoring sub-domain

This is complex, so please bear with me. We are a small company with an internal DNS server. We manage our own FTP and mail, but host our website remotely (Bluehost). We are using Mac OSX 10.3 (Panther) Server software to route users behind our firewall. I recently created a new sub-domain for a mobile version of our website (m.mysite.com). It works fine fine remotely or from a proxy server. It does not work at our office behind the firewall. Is there something wrong with my zone records?

Here is my local zone record:

Type From To

NS mysite.com ns.mysite.com

A ns.mysite.com 10.0.0.100

A ical.mysite.com 10.0.0.100

A mail.mysite.com 10.0.0.101

A ftp.mysite.com 10.0.0.103

A mysite.com 74.220.195.50 (my remote webhost IP)

A www.mysite.com 74.220.195.50

MX mysite.com mail.mysite.com

A m.mysite.com 74.220.195.50 (does not work!)

Here is an exerprt from the zone record on my remote webhost:

Type From To

A @ 74.220.195.50

A localhost 127.0.0.1

A mail 17.149.160.49 (my office's IP)

A ftp 17.149.160.49

A m 74.220.195.50

A www.m 74.220.195.50

I tried dumping local caches and rebooting all the local machines. No joy. Everything works EXCEPT m.mysite.com. Any ideas what I'm doing wrong? BTW these aren't the real remote IPs. I am using these for illustrating the problem.