An alternative for smaller operations looking to roll out the iPhone -- with support for direct push e-mail notification and possibly calendar and central contacts management -- is outsourced or hosted Exchange. For a monthly fee, companies get someone to handle their server management while providing access to all of the features of a traditional Exchange environment. It's an excellent alternative for small businesses, or even individuals who want full Exchange functionality -- and don't want Apple's MobileMe service.
There are other hosted options that rely on some of the other projects I've already cited. Both Kerio and Zimbra maintain lists of partners offering hosted services using their respective products. If an organization has a bunch of non-Outlook clients like Macs running Mac OS X 10.5 Leopard and the current version of iCal or any CalDAV calendaring solution, non-Exchange hosted services may be a better option. Similarly, Notify provides an outsourcing option called NotifyLink On Demand that lets companies maintain their current e-mail/groupware solution and deploy NotifyLink without setting up and maintaining the server in-house.
In the end, each operation will need to consider a number of factors before implementing the iPhone: the current e-mail and collaborative tool set; whether a migration is desirable -- or even feasible; the cost of deploying a new solution; and the level of support needed during and after a transition. All are likely to play a role in finding a solution. Whatever the ultimate decision, it should be made as part of a broader understanding of the pros and cons of options that go beyond simply supporting the iPhone.
That said, the number of choices means companies have numerous options beyond deploying Exchange to push e-mail to the iPhone.
Ryan Faas is a frequent Computerworld contributor specializing in Mac and multiplatform network issues. You can find more information about him at RyanFaas.com.