Hi FatSquirrel,
Thank you for the reply. You are correct and that we are trying to login with username and not email.
Unfortunately adding the account suffix does not work for us as our usernames are not the prefix of our email addresses. I just discovered from our IS group that our usernames are using the older NT format due to some legacy apps. For example, my email is [email protected] but my username is abc12.
The abc12 username is showing as the username for all of my users when importing them, but it will not allow login. I figured WordPress should at least let me use that abc12 username to login since it gets imported into the username field from the AD. But nope, it still will only allow email/password.