Ok.. I'm able to create users, I can see that I've created users, and I've done steps suggested in other threads such as adding a non-www co-domain. None of those have worked. I get "You Cannot login with the username and password entered. Please check our username and password and try again."
I've tried:
web3_username
web3_username@domain.tld
web3_username@www.domain.tld
emailaddress@domain.tld
emailaddress@www.domain.tld
emailaddress
and none will work.
Update: I figured out the problem. I had to check "Maildir" in my config.
-Adam