M476dn says SMTP username or password incorrect.

I have a brand new Laserjet MFP M476dn that I am trying to set up to scan to email. I am entering the information into the "Default SMTP Configuration" page. We have a Konica Minolta scanner here that scans to email just fine with the exact same settings (port, SMTP IP, username, password), but the HP keeps telling me "Username or password is incorrect. Ensure both user account and password are valid." I can log onto the webmail with the exact same credentials. I can't figure out why it's not working. Thanks.