Hi druscio,
Ah, yes, Intellisync is Verizon's Wireless Sync client, I believe. Perhaps someone else here who has Verizon as their carrier can add some information to this thread. Verizon support may also have an answer and they can be reached through
this page.
Though you may wish to stick with the mail program with which you're currently familiar, according to
this page in the Palm Knowledge Library, Verizon Wireless customers can install VersaMail from the Treo 650 CD included in the smartphone's original packaging.
Sincerely
Kevin