Back then one of the issues with migration then was that Exchange uses X400 format email addresses. One way to make Outlook convert to internet is to drag contacts into an email — that produces .vcf files (undocumented) with internet email addresses. In 2011 I wrote that dragging into a local PST did the same thing. Not sure that still works.
Here’s what I did recently …
- Drag and drop from Outlook/Exchange into email (undocumented export)
- From email save to desktop.
- Drag and drop the .vcf files into OS X Contacts (undocumented import.
From OS X contacts they can go to iCloud as usual.
Incidentally, i couldn’t see any way to readily import a set of single contact .vcf files into Outlook 2016. It only wanted to import them one a time. Drag and drop of the files into Outlook resulted simply in Outlook opening each one until Windows 10 die.