eM Client does work with SM chat, we've never had any issues with it since like v13, it's always worked well.

Hello Christopher.

I would be delighted if I could have a conversation with you about the settings that you are using both on EmClient and in SmarterMail15 to get chat working in Em client. We have tried everything and regardless what we do we cannot get the chat function to work,  Incidently, we also cannot get Shared calendars to work, or the Public Folders in EmClient to download all of the contacts that are in SM15.  Please let me know when you are available for a conversation and I will set up a zoom so you can see my screen and my settings.  Thank you.