[Exim] Sender: header and SMTP Auth

Hi,

I've been testing SMTP Auth locally and gotten it to work quite
nicely. Howkever, I don't want to publish the authenticated username
in the Sender header, and instead have added an encrypted header that
our abuse people can decode. I've tried setting no_local_from_check,
but it hasn't seemed to help. Any hints?

Thanks,

Gary