How do you undo the Keychain security that somehow was started on my email. Do not have a passcode.

That's an odd requirement, but I suggest you don't try to fix it in the manner it appears to suggest.

The best way to fix a recalcitrant email account (failure to send / receive alleging incorrect credentials) is to remove the problematic account, and add it again.

First remove: Remove your email account

Then add: Add your email account

Those subjects are addressed in If you can’t send or receive email on Mac - Apple Support so be sure to review that entire document.