Reading about mojo mail, one useful extension requires the host to support an email alias pointing to a script. Will that work here?
Mojo mail and email alias to script
Not easily, but you can work around this by piping to the script from procmail (see the procmail article in kbase).
Alternately, you could use a shell / ftp user that doesn’t receive any other mail and pipe the the script in a .forward file (it has to be named .forward.postfix). Then send mail for the address you want to that user.
That seems reasonable. Thanks!