I am running Act on Windows 8.1 Pro. My version of Act is Act! Pro Version 220.127.116.11, Hot Fix 1. My version of Microsoft Office is Office 365 version 15.0.
My email system is Outlook.
Mail merge sometimes works, but usually doesn't. Mostly, everything seems to merge OK with no error message, but nothing is sent to Outlook. I have no idea of why it occasionally works.