Yesterday I tested Aquamail and BlueMail with Smartermail 8538: they both work in EWS mode, but only for email. No calendar or contacts.
AquaMail explicitly states that calendars and contacts only work with EAS.
I'm also testing EM Client, but it's still in BETA and has limited functionality
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)