A user of a client computer submits a directory request to a server executing a server email application. The server email application is responsive to the directory request to identify a custom directory containing contact data for one or more individuals. The server email application determines whether to transfer a written form of the contact data, or whether to transfer both written and phonetic forms of the contact data to the client computer. The server email application indexes the contact data, prior to transfer, based on the written form when only the written form of contact data is being transferred to the client computer, and indexes the contact data based on both the phonetic and written forms when the written and phonetic forms of the contact data are both being transferred to the client computer.