When hit http://openam.example.com:8080/openam/json/selfservice/userRegistration to register new user in User Self Service, the response is code 400 with message "Unable to verify email" (see attached picture 400.png)
Steps to reproduce:
1. Add and configure Email Service (my config shown on picture email_config.png)
2. Add and configure User Self Service with Registration enabled (default settings)
3. Log out, go to login screen and click on "Create an account" link
Result: status code 400
Tested with main realm.
Could not reproduce on OpenAM 13.5.0