In the holiday email season of 2008, retailers turned up the gas on their email campaigns, hoping to salvage what was predicted to be a flat or down consumer-spending season.

Chad White's Retail Email Index shows that retailers sent a record number of emails in early December. But, he also points out, this spurt followed a flattening of the index, perhaps caused when major retailers encountered deliverability problems.

It's not clear whether this email burst caused or influenced those deliverability woes, but I would not rule it out, because an increase in frequency typically leads to more unsubscribes and a higher spam-complaint rate, which in turn reduces deliverability.

That's one of the trade-offs you can expect when you raise frequency beyond your subscribers' tolerance level, and one of the reasons I always caution marketers to manage frequency expectations even before the subscriber relationship begins.

Finding and Managing the Balance

You need not restrict yourself to a meager diet of one email message a week. After all, your email program has to meet business objectives, usually by driving revenue. Also, emailing too infrequently will hurt your email program almost as much as pounding your list into oblivion.

So, you must strike a balance between sending out enough email to help you meet or exceed your budget numbers and sending so many emails that you trigger a mass revolt on your list via spam complaints or unsubscribes.

Increased frequency has real and hidden costs, too. In addition to the obvious budget resources you consume—staff time, content development, messaging software expenses—the less-obvious cost of list churn results when people turn against you: unsubscribes, spam complaints, and the silent enemy: inactivity.

Why Targeting Is Important

At a recent email conference, some marketers shrugged off the cautious approach to managing frequency. One said he doubled frequency at less cost and saw a huge increase in revenue.

But this marketer (in the entertainment industry) was sending emails to a highly engaged audience that had made previous purchases and was very likely to be interested in related offers. His program was not simply sending more of the same, but targeting emails based on customers' preferences and buying history.

Targeting increases relevance. With increased relevance, you can afford to send more—to increase frequency—because your chances are higher that your subscribers will welcome these emails that clearly reflect their interests, wants, or needs.

Still, it is critical that you think beyond email as simply sending out offers. Email gives you a vast array of message options that can let you boost frequency without sacrificing deliverability or the customer relationship. That leads to the next stage in the evolution of email marketing.