Then what I'd suggest is checking whether those things that are announced as "Other suggestion" might actually be in your Contacts/Address book. Things that are resident there will never be easily purged from autocomplete unless they are first purged from contacts.
This can be insanity making when, in cases like Gmail, they create a "behind the scenes" category of Contacts where anyone you've ever sent or received a message from that you didn't mark as spam gets added to the "All Contacts" category, which most people have no idea exists. If this is being synced into Outlook (but not vice versa) things can get even more insane.
Brian - Windows 10 Pro, 64-Bit, Version 1909, Build 18363
Tolerance is the positive and cordial effort to understand another's beliefs, practices, and habits without necessarily sharing or accepting them.
~ Joshua Liebman