[opendmarc-users] Initial user questions

[Alex]

Hi,

I'm attempting to implement DMARC for my domain and have a few
questions. I have a fedora system with
amavis/postfix/spamassassin/dkim/spf configured.

  - If both SPF and DKIM are configured, which does DMARC use to
authenticate? Can a system with only an SPF record still use DMARC, or
is DKIM also necessary?

  - What actually does the quarantining with the sp= option? Would it
just be a variable that is set for something like spamassassin to
interpret?

  - If I don't want to be a DMARC compliant receiver, do I need to run
a DMARC server locally?

  - I realize this is opendmarc, but it seems the server options for
Exchange in a medium to large organization are very limited. Do people
generally front-end their Exchange systems with a Linux box running
opendmarc? It seems to be the same with DKIM and Exchange.

  - Is there anything specific I should know when trying to implement
it to protect my users from receiving mail purporting to be from my
own domain?

Thanks,
Alex