Using recipient_filter with Sender Data

[ghost]

From what I can tell, it is not possible to use recipient_filter to disallow certain recipients based on the sender's data. For example, if the sender's email address is john@example.com and I only want the sender to be able to send messages to other users who also have an @example.com email address, there doesn't appear to be a way to do this. I think this would be a useful addition to this great Django package.