Call Pilot Message Notification Question

[gibsonLP]

Good Morning,

I am recieving a follow up message in my mailbox that says, "The system was unable to reach the number for Message Notification." It will send this message after a message has been left in my mailbox AND my pager goes off to notify me of a message. Does it leave this secondary message if I do not listen to the message left within a specified period of time or is it a setting in the 'Class Of Service' that needs to be configured?

Thanks
GibsonLP