Remove Addresses From the Auto-Complete List Windows 10 mail app

Along with many others, I have been fighting this vexing problem. Here's what finally did the trick for me, based on piecing tips together from others.

1) EXHAUSTIVELY search all your e-mail folders - ALL OF THEM, TRASH, SPAM, INBOX, ARCHIVES, everything - for e-mails that contain the bad address.  Remember that if the bad address was one of several in a message, even if it bounced the address is still part of that message. And it might be in a reply that was sent to you.

2) Delete EVERY LAST ONE of the messages with the bad address. The ENTIRE message. If it's something you really need to keep, copy-and-paste the contents into a NEW message and send it to yourself. DO NOT JUST FORWARD THE MESSAGE to yourself or elsewhere - the bad address will still get dragged along with it. Make sure you do not copy headers - body text ONLY.

3) Double- and triple-check what you did in steps 1 & 2 so you're not wasting time because you missed one.

4) Log in to outlook.live.com and delete all of your contacts there. I am not sure this step is really necessary, but it was included in one of the other sources I used and it's not going to hurt to do it even if it's not necessary.

5) On Windows, do Settings|Apps|Mail|Advanced Options|Reset. 

6) On Windows, do Settings|Apps|People|Advanced Options|Reset.

7) Restart your computer.

After doing all this, I found that the bad e-mail address was GONE. So were a number of others, which I presume had been in my e-mail folders at some time but which had no traces left by this time (i.e., a bad address in one or two messages that had long since been permanently deleted.)

It appears that Windows Mail is populating the Auto-Complete cache using ALL e-mail addresses that are present in ALL of your messages in ALL of your folders. So if you eliminate every possible trace of it and reset the Mail app, it has to rebuild the Auto-Complete cache and doesn't have any instances of the bad address to pull in.