Try this:
Go in and set up an account for your pager. Call it User.Pager@somedomain.com.
Set that account to forward all e-mail to the pagers "real" e-mail address. (ie pager-pin@pager.net) Make sure you leave that account locked, there is no reason it should log in.
Next set up a group called admin.alerts. Assign both your userids (User and now User.Pager) to that group.
An e-mail to admin.alerts@somedomain.com, should now go to both addresses.
Finish up by going in to the "Other e-mail settings" portion of the server-manager and putting admin.alerts@somedomain.com in the box labeled "Forwarding address for administrative notices:" at the top of the screen. Save your changes and you should be good to go.
Hope that works for you.
-Dave