Rerouting message sent to temp email address to real email address?

Similar to craigslist, how can I manage emails so that any email sent to one address is rerouted to the user's correct address?

When an ad is posted, the poster is given a temporary email address (ie. 102928842@mysite.com). The ad will display that temporary email address as the seller's contact information. Any email sent to this temporary email address should be rerouted to the seller's real email address.

Is this possible?
I'm using VS2005, ASP.net 2, sql server 2005, C#

Thanks.

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