Take salt with salt. This is far beyond my own experience, but I must crack this generosity!
A quick look at the available Google APIs tells me that you're out of luck doing this programmatically with their APIs. But I can look at the wrong set of APIs.
What you can do is delete mail through IMAP. How IMAP features apply to Gmail is given here.
How to configure IMAP for google apps / gmail here
Unfortunately, there is no way to set this parameter for the entire domain. If this is a problem, then you may have to use some kind of product for web automation. And if you are really crazy, you can start your own simple machine, which performs only the required click (enter your username and password, and then two clicks to enable imap).
So, if you manage to configure IMAP on accounts that have fictitious mail, and you have a way to get the username and password of each infected account, you can use the IMAP library for .NET to delete them. Cm:
Access to Imap in C #
using C # .net librarires to check IMAP messages from gmail servers
It seems like it should be easier, right? Sad face.