[MlMt] Have Calendar.app use MailMate rather than Mail,app?

[Randall Gellens]

Is there a way to have Calendar.app use MailMate to generate replies 
rather than Apple's own Mail.app?  (I don't see the Mail.app UI, so 
perhaps Calendar uses a library of it.)  If I accept/reject a calendar 
invitation, the reply is always from my default mail.app account, and 
contains headers indicating it was generated using mail.app component:

    Mime-Version: 1.0 (Mac OS X com.apple.MailServiceAgent 11.0 
\(3445.9.1\))
    Subject: Event accepted: Test event
    X-Mail-Calendar-Part: Yes
    X-Mailer: Apple Mail (2.3445.9.1)

It drives me crazy that someone can send an invitation to a work or 
other non-default email address, and any reply comes from my default 
account.

--Randall