1. A wireless communications system comprising: a plurality of wireless communications networks; a plurality of mobile wireless communications devices for sending and receiving wireless electronic mail (email) messages over said wireless communications networks; and a resource deployment server comprising a database module for storing a plurality of resource deployment packages (RDPs), each RDP comprising carrier specific deployment content and deployment instructions therefor relating to sending and receiving email messages, each RDP also comprising a resource identifier (ID) associated therewith, a plurality of proxy modules for interfacing with respective ones of said plurality of wireless communications networks, and a deployment service module for cooperating with said database module to notify said plurality of proxy modules to retrieve the stored RDPs, and to deploy RDPs to said wireless communications networks via said plurality of proxy modules to update deployment content thereof based upon the respective deployment instructions and the associated IDs.