Reputation and Authentication are two terms that are very important to the messaging community, although the definition of either term may vary depending on the point of view of the person using the term. Here we'll define the terms as we use them so that you as a sender can understand what we mean when we use these terms.
For inbound mail, Reputation here currently is solely IP-based. An IP's reputation will be determined based on its sending history (volume, spam filter rates, complaints, etc.). High volume is not necessarily a bad thing for reputation, but irregular patterns to one's volume can be a contributor to a poor reputation. Similarly, low or non-existent complaints do not necessarily mean a good reputation; our customers can only complain (i.e., report as spam) mail that's in their Inbox, and if most or all of an IP's mail is being delivered to our customers' Junkmail folders, then the IP will generate few complaints.
As for Authentication, we are aware of technologies such as SPF and DKIM, and are studying how best to use them at this time on our inbound mail stream. We are interested in taking advantage of domain-based authentication technologies to allow senders to establish and maintain domain-based reputations, but we are not in a position to do so at this time. When we are in such a position, we anticipate that while authentication technologies will be useful in establishing the legitimacy of the source of a given email, authentication will not by itself convey to the sender a good reputation; any sender can authenticate its outbound mail stream(s), but an authenticated sender's reputation here will still be determined by whether or not our customers want that sender's mail.