We have an SBS 2003 Standard Domain Controller and until recently were using Blackberry mobile phones for some staff. Email was being successfully sent to the BB's - this being configured using the BB website configuration (I think this is actually a 'pull' email setup).
We have recently purchased 2x iPhone 4.
It took some doing, but I was able to get Exchange to sync Outlook with these 2x iPhones using the EE article by alanhardisty, "Exchange 2003 - Activesync Connection Problems FAQ". This is a brilliant article and got it working after trawling the Internet for ages and failing repeatedly.
So, we are now getting email to the iPhones happily, but it only works while out of the office where the SBS server lives. When the iPhones are out of the office they connect to the Internet via the 3G mobile connection and they sync with Exchange fine, but while in the office they connect to the in-house wireless LAN as well and then they won't sync. As soon as they go out of range of the wireless LAN they start to sync again.
So there must be a setting or something somewhere that I have overlooked.