The ability to test and track results within emails makes it a compelling marketing channel, providing the ability to continually improve on previous results and bump up that magic acronym: ROI. In the current challenging economic climate, testing isn't a process many marketers can continue to ignore -- it's become a necessity.

My last EmailInsider column ("Email Industry Disagreements: Where Do You Stand?") touched off the start of some good debate over single vs. double opt-in (also called confirmed opt-in) that went beyond the usual arguments (list size vs. list quality).

Dear Email Diva: I'm compiling an overview of the common email metrics, specifically the performance over the last year, trends, etc. I was trying to find statistics to support the statement from this post by Lynn Terry that "unsubscribe rates are at an all-time high in the online business & marketing niches. In fact, April through June of 2008 saw some of the highest unsubscribe rates."

I thought I'd follow the Email Diva's approach this week and pose a question that was asked of me a while back and the associated response. Question: How do you really show the effect of email on the business? We track open and click-through rates, but revenues are mostly generated through store-level transactions.

ou can learn a lot from watching your peers, especially during the critical holiday season period. During the fourth quarter of last year, I tracked more than 3,300 promotional emails from the top online retailers through the Retail Email Blog. Based on that monitoring, the Email Experience Council has produced the Retail Email Guide to the Holiday Season to serve as a helpful roadmap to the email holiday season. Here are four tips from that Guide that will set you on the right track....

Every time I speak at a conference, there is usually at least one person who raises their hand, or if there is no time for questions, they come up to me after the program and ask the inevitable question. It is not always the same question, but usually some derivative of, "What is the average ________?" You can fill in the blank with anything from open rate to click rate or delivery. I have never worked in an industry so fascinated by the concept of industry averages.

I didn't realize how lost I was in proper society until I read Judith Martin's "Miss Manners' Guide to Excruciatingly Correct Behavior." Turns out that the polite way to eat asparagus is with your fingers -- who knew? Miss Manners knew, luckily. The book is brimming with information even more useful than asparagus etiquette, too, and we'd do well to take her advice into account when crafting our email programs.

After 15 years or so of marketing via email, a solid body of knowledge and best practices is evolving, based on both experience and research. However, the industry still hasn't reached consensus on a number of fundamental precepts in email marketing. In these "debates," followers of each side often make compelling, even impassioned, arguments why their view should prevail. I initially came up with a list of about eight disagreements, but narrowed it to three biggies due to space constraints. (I'm saving the biggest debate -- "permission is required" versus "CAN-SPAM doesn't require permission" or "reputation supersedes permission" -- for …

The behavior of most email subscribers proves that the promise of email marketing is still more appealing than the actual email marketing received. Think about it. Lots of people opt in. Not many subscribers are active. The variance in those two numbers is what I call the "optimization opportunity" for your program.

Dear Email Diva: I just read your post about sending email to tradeshow attendees, and was wondering how you feel about sending to tradeshow attendee lists provided to exhibitors, in light of CAN-SPAM. Do attendee lists like those fall under "implied" permission, or should they be considered opt-ins? Seems like a gray area to me. Obviously the safe bet is to use only names you've collected directly at your booth, but then you may miss out on the opportunity to email attendees who didn't "drop a card."