I'm late to this thread, but what we have done successfully is to use good old Microsoft Word mail merge using Outlook. We export the source list from Access, link the Word merge template to it, and go. This avoids any complex VBA coding or use of OLE automation.
This does require Outlook Classic still, I believe.
Since Outlook Classic supports multiple profiles, it is possible to create a distinct profile for whichever organizational email account you are using to send the bulk mail. We launch Outlook into that profile before executing the mail merge.
Lo-fi, but it works.