You can't do that with SmarterMail 16 Professional.
You need a more recent version of SmarterMail with MAPI/EWS support activated (so you need a Enterprise license + MAPI/EWS license...)
Older version (and Professional...) doesn't support MAPI/EWS.
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)