There is no built-in support for GroupWise on the iPhone. Apple supports a number of other services, but GroupWise has not been high on the priority list and honestly, I don’t know that it would be high on mine either… Having said that, it did pop up on my radar and I was able to find a couple of ways to achieve a good sync. The first is Entourage. You can use Entourage as a conduit to then grab information and sync it with GroupWise. This has a hopefully obvious disadvantage, which is that it does not synchronize wirelessly – you have to cradle sync to get the data onto the iPhone.
The second and third options are outsourced services that just handle everything for you. Of these, GroupWise Sync is a great option (they have a free version that just grabs mail or pay-per-month for contacts and calendars) as is the monthly version of the CompanionLink GroupWise sync. CompanionLink has a separate desktop client, but much of what it does can be obtained by using GroupWise 6.5 along with Office 2003 and iTunes to synchronize contacts and calendars while cradled.
Finally there’s NotifyLink, which works with Exchange, Kerio, Gmail, CommuniGate Pro, FirstClass, Scalix, Zimbra and about anything else you could ask for, providing synchronization services to iPhone, Palm, Windows Mobile, Blackberry and Symbian. In short NotifyLink is the Swiss Army knife of the mobile sync world. Take anything, sync to pretty much anything else, for a monthly fee. Just make sure your users look at the results before you put it into production en masse as it is a little different than the standard screens they’re used to seeing in some cases…