My client registered an email address on Google as
email@example.com using the Google API. Later he registered the domain
example.com at MochaHost.
I have then created another email address
firstname.lastname@example.org over the hosting space (not on google) using control panel.
I am then using
email@example.com to send emails to his customers. The emails are successfully sent to all customers.
The issue here is that the client wants a notification email to be sent to his email address
firstname.lastname@example.org also (while it is on google). When I try to send email to this address, it bounces with a "mailbox not available" error message.
As far my understanding goes, I think this is happening as the domain name is same in
email@example.com, so considering the same domain it tries to send the mail over the same domain whereas webmaster does not exist in that case.