Can you formulate that question more precisely if this doesn't answer you?

* I am still using the same domains that I've always hosted mail for * Since I am sending from new IP addresses, but want to retain the ability to send from the old MTA until it is decomissioned, the new MTA uses a different HELO identifier, and the dependencies for that are all in place (forward and reverse DNS addresses and updated SPF records) * The new DNS records are still in the same administrative domain as the old ones