RECENTLY I HEARD THAT EMAIL as an industry is worth $10 billion. Not bad after only 10 years or so, if you buy into that number. As our industry approaches maturity, I believe we are on the verge of a new phase of evolution. Now is the time to get ready for it.

As we know, email means different things to different people. As a business marketing tool, it often gets confused with advertising channels. But it does represent a medium for sales, marketing, customer service, channel service, technical service -- and the list goes on.

Email has a front end we call acquisition or engagement, an intermediate stage we call conversion and a back end that we call retention or loyalty. When you combine all the systems and views of the customer, we call this eCRM. That's our business in a nutshell.

Trends show we are shifting to "touchpoint" views of a customer. Every touchpoint can be leveraged to improve the brand relationship with the customer and should be afforded the same weight as others --including email.

The industry has spent two years trying to address deliverability. This makes sense, since landing in the spam folder (if it lands at all) has brand and revenue consequences. Yet after all this time, many are still confused about what deliverability is, whether it can be bought, or if it needs to be earned over time.

I'm encouraged by the many discussions around trigger messaging, lifecycle messaging and being smarter about targeting and timing of email in general, but so few can actually see the entire picture of a customer experience that this is often an endless discussion.

While there's been a lot said about mobile messaging and RSS, we are still in a conundrum about these channels and media. We can't even tell if SMTP-based email is being read on a desktop, laptop, BlackBerry or smart phone. RSS has found its home, but people are still struggling with its monetization and its relationship to email. Should it replace email? Can it be tracked like email and managed in common environments without creating new processes for an already overburdened staff? Will the self-subscribing nature of RSS be the "profile management" the email industry has been seeking for years?

Here's what I see coming our way over the next few years. All these ideas are up for debate.

Most of the personalization and cool dynamic content sent through email will be reserved for the highly engaged, responsive, highly valued consumer. If you don't open or click over time, you'll quit getting email from the brands and sites you signed up for. ISPs are already recommending that we only send to customers who have bought something or have long-term relationships with. I see marketers really focusing energy on that highly engaged audience, while the infrequent or non-responders will be left to sign up again or get less email.

Email acquisition will be done on a contingency basis (pay to perform). Engaging new consumers through email is not easy, and I see this entire process extending from rented lists to a sequence of communications to hand-raisers within a list, rather than a broadcast message hoping to catch them at the right timing. I don't know that the list owners will survive on a purely CPM model with so many lists to test without becoming more accountable for a "conversion."

Email priority delivery will be a paid-for service. While anyone close to the space knows you can't discount the importance of managing delivery and your delivery reputation (spam complaints, bounces, clean files and practices), you can't deny the value of priority delivery. I don't think reputation alone will make it in the future. I liken it to FedEx on some levels. So, you either pay to get email delivered, or you will pay in other ways trying to get it delivered and prioritized. Either way you will pay more than you are paying today. Look at how the ISPs are beginning to monetize their email lists, ensuring priority delivery to those advertisers that rent those lists.

Email marketers will be forced to split their forces to address RSS. This may become a new department or an extension of the Web team. RSS is a content game. The self-subscribing, real-time nature of RSS will make it easy to organize content, but it will still be a challenge to pull content together and syndicate it, not to mention measure interactions with it. Imagine doing this with the email team that is already a few horses short of a herd.

A few wild-haired premonitions -- and open to others. But hang on to this, and let's see how many of these ideas we are talking about at the end of this year.

David Baker is vice president of e-mail solutions at Avenue A/Razorfish. Visit his blog at http://whitenoiseinc.com