Need ability to notify an external email when email arrives at internal email

Hello.  I am an IT provider for many small businesses.  I have one client (we will call them "Expert Tech") that has "contractors" who perform periodic work on behalf of Expert Tech.  The contractors each have their own email addresses associated with their personal business with various email domains such as @contactor.com.  My client (Expert Tech) has an Exchange 2010 server with an email address domain of @expertech.com (as an example of course).

Here is what the client needs to happen:

1. Someone sends an email to contractor_bob@expertech.com and it arrives on the Exchange 2010 server
2. Exchange 2010 sends a notification (not a forward) to contractor bob's personal email at bob@contractor.com, and this notification just needs to let contractor bob know to check his @expertech.com email. 
3. This needs to be a server side and automated solution. 

The reason for this is that contractor bob only does periodic work, perhaps once ever 3 months, for Expert Tech, and therefore will not keep his @expertech.com Outlook Web Access open all the time.  In fact, contractor bob may never open his @expertech.com email unless he gets a notification. 

Here are things I've looked into:

• Create a transport rule to send an event to Event Viewer, and then have the scheduler pick it up and email a notification (this works for Exchange 2007; however I cannot find the transport rule to make it work in 2010).
• Create a rule in Outlook Web Access to reply a specific message to bob@contractor.com (this works except that it also sends a reply to the originator of the email, and that is unacceptable.)
• I have also looked at a host of other methods such as forwarding with attachment, journaling, and tons more; however they all end up sending a copy of the email to the bob@contractor.com.  By company policy, no email may automatically leave the @expertech.com system in this manner.  Only a notification is allowed.

This seems like something that should be very easy to do, and in fact there are many webmail hosts that have alerts by defult in them.  I cannot find it in Exchange 2010. 

Any help is greatly appreciated.

Thanks...Mike