My use case is a 501c3 organization with an associated 501c4 (sorry this only makes sense to US folks!). They have all the same contacts but need to keep c3 emails separate from c4 emails--most important, sent from different domains. It is possible to do this from a single Civi instance (i.e., have the addresses available to send emails be on two different email domains)?

Because all the contacts are the same they REALLY don't want to maintain two Civi instances. (Note we are in the eval stage so this is not a Q about how to do it; at this point I am really just looking to know whether it's possible.)