Amazon SNS requires you to verify your PagerDuty service's email address. If you send a confirmation email to your service's PagerDuty address, you will be able to view the message body and verify that address from the PagerDuty console. To do so, find the incident that is created by the email and view the message to verify the email address.
To view the message from the Incidents page, click on the Details link:
You can also view the message by going directly to the incident's log.