I have deployed an app on Google App Engine ending with 'xxx.appspot.com'
It has a 'Contact us' form. The sender or the field 'from' only allows recognized email addresses (people who are associated with the app, like developer, admin, owner etc), otherwise it gives an error after clicking on 'send' button.
I have hosted this Google App to a custom domain (using Application settings from Dashboard). But cannot make 'Contact Us' form to work due to above reason. Ideally, anyone can send an inquiry (a valid email address that is), but as I said only 'recognized' emails are working.
Can anyone provide any insight - what should be done?