[thelist] Email-triggered db activity

[David Shadovitz]

A potential client wants his web site's database activity to be
triggered upon receipt of email from his credit card authorizer, not by
submittal of a form.

That is, a customer places an order on the web, which sends the info to
the credit card authorizer.  The credit card authorizer then sends email
to the client.  The client wants to have the receipt of this email
trigger the necessary database activity, such as decrementing the
inventory of the ordered item.

Anyone do this?  Any advice on the mechanics?

Thanks.
-David