Send calendar invitations from the user's e-mail address, not email@example.com
Currently when I invite a non-fruux user to a calender event the invitation comes with:
From: <User's Name> (via fruux) <firstname.lastname@example.org>
It would be much nicer to be "From:" my real e-mail address.
I believe this "From: ... <email@example.com>" was due to mis-interpretation of SPF. SPF matches the envelope sender's domain (typically in the "From " header -- note the lack of colon after that -- it's usually the first header in an SMTP delivered message), not the author's (who is in the From: -- with a colon) domain.
You should have no problem sending e-mails with a From: of any domain you want. What is important is that the envelope sender is an @fruux.com domain. This is what you want anyway because this is where bounces are sent back to.
Michael Kliewe commented
You cannot send emails with "any domain you want". There are things like DMARC out there, which check the From:-header, and then use that domain and check SPF and DKIM.
What fruux does is totally correct, they use their own domain as a sender address (envelope-from and From:-header).