Alex,
Thanks for getting back to me. I'm running Windows Server 2003/Exchange Server 2003 I didn't install URLScan because I read it wasn't needed due to the enhanced security features of IIS 6.
AT&T Wireless is my service provider, on my Sony Ericsson T616 under "Connect > WAP Options > Security > Trusted Certificates" I have the following 4 certificates listed:
Verisign
GlobalSign
CyberTrust; Baltimore
Entrust.net WAP
I have a test certificate from Verisign however the Issuer is different than that of a regular Verisign certificate. I don't really have a spare $300+ to spend on an SSL certificate from one of these trusted authorities and thus far I have been unable to find out how to add Trusted or Client certificates to the phone. Naturally I would rather not access OMA without SSL
Simon