🇺🇸United States @IVNate

@patrickharris

I have exact same issue.

1. configure smtp module via settings.php
2. go to /admin/config/system/smtp
3. send test email
4. Receive "You must enter an SMTP server address" validation error.

Two potential solutions:
1. As you mention, move test form to a different tab/page.
2. Change form validation so it recognizes fields that are set via config and do not validate them.