The thought of blogging predictions for the New Year in Deliverability makes me cringe. I’m not exactly sure why; it may have something to do with the fact that everyone else has already done it – we’ve had a bumper crop so far this year. Mostly, I think, I’d hate to be proven wrong later. So, instead of offering my own predictions (which would doubtlessly sound much like anyone else’s), I’d like to take a look at two different trends in deliverability that came only half-true in 2010, but that are still worth your time to continue to watch in 2011. The two trends are Domain Reputation and Engagement Metrics.

If you can recall what it was like to switch mobile carriers before the winter of 2003, you’ll understand why domain reputation is a big deal. If you wanted to switch carriers then, you had to get a new mobile number, because the local number portability rules for cell phones hadn’t yet been enacted. Coworkers, friends, relatives, and vendors all had to be notified of the change if you wanted them to stay in touch with you. It was a royal pain — painful enough in many instances to keep folks from switching carriers in the first place.

Today, sender reputation is largely associated with the IP address from which e-mail originates, and not with a business or brand. If a sender wants to migrate their e-mail program off of the desktop onto a hosted platform (like Real Magnet), or change ESPs, they’ll have to leave their sender reputation behind and start from scratch because the move means they’d be sending from an entirely different IP address.

Domain reputation is like local number portability: a reputation score is associated with sending domain (e.g., mail.yourbrand.com) instead of a dotted quad (209.108.90.17). On an Internet in which reputation is assigned to a domain rather than to an IP address, sender reputation can follow the company or brand, for better or worse, across changes in originating IP address.

Domain reputation was one of the hot new things that was supposed to gain traction in 2010, but that mostly didn’t. To be sure, ISPs are filtering on domains and URLs in the content of e-mail messages (for sites that are known to host malware or to be associated with spam, for example) but that are not necessarily domains that belong to the sender. Some of the big free inbox providers use their own, internal sender domain reputation systems for filtering, but these are still miles away from the kind of granular reputation scoring data that is available for IP addresses.

One key reason why domain reputation hasn’t enjoyed widespread adoption is because it relies on the use of sender authentication protocols to tie reputation to the sender, and lots of senders aren’t bothering to implement those protocols. But just last week, the smart folks at Gmail announced that businesses who host their mail on Google Apps can use DKIM, a particularly flexible authentication protocol, just by ticking a box in their application settings. If other large mail hosts follow suit, domain reputation has a chance to pick up steam in 2011.

The other prediction that became only half-true is the broad adoption of detailed engagement metrics by ISPs for automated deliverability decisions. Hotmail and Gmail made a huge splash last year by incorporating some engagement metrics in their filtering processes. Priority Inbox at Gmail, and Sweep at Hotmail/Live give preferred delivery – and even preferred positioning within the inbox – to mail that the recipient has opened or clicked through from before.

But beyond those two standouts, and only in a fairly limited way, none of the other large ISPs or reputation scoring firms seems to have done much more than experiment with collecting and using the data. The incremental improvement to their existing filters does not appear to have justified the huge overhead associated with the collection and management of all the additional data. For a time, we’d heard that ISPs were measuring all kinds of engagement metrics – like social network sharing activity, and even how long a recipient appears to spend reading messages from a given sender. But beyond the opens, clicks and spam complaints, other engagement metrics just don’t seem to be all that much more useful for deliverability.

That’s not to say that senders don’t need to worry about engagement – engagement remains incredibly important. Those clicks, opens and complaints remain significant components of sender reputation. Tracking engagement is critical to improving ROI. Senders who perform even a modicum of content or subject line testing gain incredible insight on how recipients are interacting with their mail, and can learn much about what will generate the best conversion rates. But when it comes to getting into the inbox, detailed engagement metrics do not appear to be on track to becoming as important to recipient domains as blocklists, content filtering, and IP reputation scores.

Detailed engagement metrics and domain reputation scoring are two big trends of 2010 that happened only half-way. But don’t get me wrong – they remain important concepts for deliverability, and successful senders will keep their eyes open for broader adoption in 2011.