John Mertic passed along a note about a new post to the SugarCRM developers blog detailing how to enable IMAP support for PHP on an OS X machine.

With the release of Mac OS X 10.5 Leopard last fall, Apple (finally) included a modern version of PHP (currently version 5.2.6 as of this writing). [...] However, the default install of PHP that Apple included didn't include all of the available PHP extensions. Most notable is the IMAP extension, which is used in SugarCRM for the Campaigns and Emails modules. However you can build this extension and have it loaded dynamically, without affecting the rest of the default PHP install.

He shows where to get the packages and libraries you'll need to get the support working. The method involves building a shared module and including it to be loaded in your php.ini. This way it doesn't disrupt anything the current build has and you don't have to recompile everything over again.