[Mailman-Users] how to identify subscribed address?

[Andrew Watson]

A subscriber has asked to be removed from my list.
The addresses he suggests are not subscribed.
I asked that he forward an example of a received message, 
with all headers visible,
so that I could identify the problem address.
But the subscriber address does not appear anywhere in the headers.

Is there a way to figure out the problem address?

-Andrew