iPhone (and all smartphones) doesn't support MAPI.
With smartphones (Android and iOS) you can use EAS to sync all data, but you have to configure SmarterMail for EAS (and buy the EAS license, of course...)
Gabriele Maoret - Head of SysAdmins at SERSIS
Currently manages 6 SmarterMail installations (1 in the cloud for SERSIS which provides services to a few hundred third-party email domains + 5 on-premise for customers who prefer to have their mail server in-house)