I'm using Virtual Box, with three Virtual Machines:
1 for CentOS 7 (with the iRedmail)
1 for macOS Sierra (Outlook 2016 for Mac) uses naturally .olm file, but I can't export to .pst
1 for Windows 10 (Outlook 2016 for Windows) Working perfectly with the server.
Now I facing the "5.7.0 Must issue a STARTTLS command first" on my Outlook 2016 for Mac, I can't send a simple mail to my iredMail server (I have the .olm file in this application client).