When a valid user send an email to Jira to open a ticket it creates the issue by which the user gets notified with the ticket details via an incoming email.

However, if a non-customer email sender sends an email request to open a ticket, the Jira Service Management Mail Handler simply rejects stating " Signup is not currently available", without sending any notification to the user via email.

Hence, it would be great to send an acknowledgement stating the email address used is not allowed to create an issue in this project.

Screenshot are shared above for reference.