iPhone 3GS connectivity to SBS 2003 Exchange Server Problem

[Number6]

Strange one this.

 

One of our users with an iPhone 3GS on Orange cannot connect to Exchange on the SBS 2003 box. I've looked at the phone, in fact I have it here now, and cant see any problem with the settings. I've even deleted and recreated the account on the phone.

 

It's not a problem on the network side because I can connect via my Android phone and we have one other user who's iPhone 3GS connects flawlessly, it's on O2. Exchange account settings are the same on all the phones.

 

I'm out of options - is there some unrelated setting on the iPhone that I need to change? Is it an Orange issue, blocking ports or something?

 

Basically..... HELP, please?