I make intensive use of Office autocorrect feature for fast typing (which I use as a kind of autocompletion - shorthand / stenography). I have been able to modify the ACL file for Office 2011 applications (which works great in Word), but Office 365 comes with a separate 2015 version of Outlook and I cannot find the dedicated file for autocorrect entries.
After a few tests, I found out that Outlook does take the Mac OS system dictionary entries into account (which are stored in an .sqlite file in /Library/Dictionaries/CoreDataUbiquitySupport/username/UserDictionary/local/store/UserDictionary.db - in case you're wondering where it was...). So I have been able to add my own dictionary entries in this sqlite file and Outlook does take them into account. Heck, Outlook gets real slow when this system dictionary is fed with more than 3000 entries (I bet you're wondering wtf is in this list, never mind).
Luckily, I found out that Outlook's Autocorrect feature also uses its own set of entries (which can be manually updated through Outlook Preferences > Autocorrect) - these work better and faster. So now I just need to find this damn' little file where I can store my huge list of words through a bulk import…
A long search on the Web made me realize I am probably a very lonely user of Outlook's autocorrect feature (at least on Mac)… Any weird guy like me out there who would incidentally know the path to this golden little file?