Yes, if you use with a cloud Exchange server (eg, MS365...) it can be a bit slow, but it works pretty well...
And if you have a local on premise Exchange server it's pretty much faster.
The local on premise option is what I'm looking for...
Gabriele Maoret - Head of SysAdmins and CISO 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)