How to Find Emails Received From a Specific Account?

Hi,

I have set up so that whenever a customer make an order, the eCommerce system will send two copies of the order email to the following two email accounts separately:

a@ myemail.com

b@ myemail.com

Now I want to remove the duplicate emails. I check the headers of the emails. The only difference for two duplicate order emails is below:

The one sent to a@ myemail.com:

Envelope-to: a@ myemail.com

Received: ...

               for a@ myemail.com;

The one sent to b@ myemail.com:

Envelope-to: b@ myemail.com:

Received: ...

               for b@ myemail.com;

So, how to find all order emails sent to b@ myemail.com and delete them?

Thanks