Sharepoint sending email to

Users report receiving bounce back email 
generated by Sharepoint

Sent: 1/1/2015, 12:00 PM
Subject: Undeliverable: John Doe wants to access 'Site Pages'

Delivery has failed to these recipients or groups:

A problem occurred during the delivery of this message to this e-mail address. Try sending this message again. If the problem continues, please contact your helpdesk.

Each Sharepoint site collection can set its own email address for access requests. If enabled, the default notification email is

Go to the top level site of any site collection.
Click on Site permissions on the settings page.
Click Access Request Settings

Either Change the default value to whatever email you want to receive the access requests or unchecked the box " Allow Access Requests"