Broadcast service provider email caught in Postini

I have a client that uses an external service(Publicaster) to send out business related broadcast email messages.  Most clients receive these without issue.  This Publicaster allows my client to send the message as if it were coming from her own domain(user@abcinc.com) instead of user@publicaster.com(or whatever they use internally).

So I have two questions;

First the issue I'm running into is messages to these services get cause in my clients own Postini account when they cc themselves on the broadcast messages.  I understand why they are getting caught, Postini thinks Publicaster is spoofing us.  However if I whitelist their own email addresses then I open them up for real spoofs that we would want blocked.  Have any of you dealt with this situation and is there a way to allow these messages in without opening a dangerous hole in their spam filter?  I was thinking maybe if I could contact Publicaster, get their IP range and then either whitelist that range, or possibly add them to an SPF record?

Secondly, how do these broadcast services get around rDNS lookups for the external domains my client is sending to?  Don't those domains do an rDNS lookup and would see that Publicaster is not registered to abcinc.com?  Or do those services actually go through the trouble of setting up rDNS.  I assumed there would need to be some sort of authorization to register yourself as a specific domain.  I guess I'm looking for some clarification on how these broadcast services function and are able to get messages out without being blacklisted or the messages just dropped since they are not coming from the actual domain of the sender.

Thanks,
Mike