How to Fix Apple Mail Can't Connect after O365 Password Reset: "Unable to verify account name or password"

Following a password reset (specifically a Microsoft O365 account), Apple Mail was not happy.

It recognized that the password had changed but wasn't accepting the new password, even though we knew the password was correct.

"Can't connect to the account...Enter the password for user...Unable to verify account name or password..."

The user was specifically running Mac OS 10.14, though this fix may work just as well for other Mac OS too.

Here are the steps that worked to fix this:

1. In Apple Mail, go into Preferences->Accounts->uncheck enable this account. Quit Apple Mail
2. Go into System Preferences->Internet Accounts->the email account->Enter the new password here
3. Reopen Apple Mail, and re-check "enable this account" in Apple Mail. The status circle should light up green and say connected, but the account still might not be showing in Mail (e.g. the inbox, subfolders, etc.).
4. If so, quit Mail.
5. Re-open Mail. The account now appears but there's a new error / exclamation point appearing, but it's simply that the account is offline. Click the error/exclamation or go to the top menu->Mailbox->Take All Accounts Online and back in business!

***For step 2, I alternatively did test re-entering the password in Apple Mail directly in the password field in Preferences->Accounts->the email account->Server Settings and that also seemed to work just fine. But I like the idea of entering the password in Internet accounts instead just for good measure since that's where the calendar, contacts, etc. login info lives..