• by George Bilbrey , Op-Ed Contributor, July 30, 2013

No matter what you’ve heard, “Mail less” is not the official motto of deliverability experts. “Mail as much as your subscribers want,” is more like it. We work in email marketing: We know that more mail means more money. But we also know that more bad mail -- mail subscribers don’t want -- means bad inbox placement, and that means less money.

Our most recent survey of global inbox placement shows how hard it is for marketers to get this right. Reaching the inbox isn’t getting any easier for most of the world, but we’re seeing more senders that consistently make it. They’re not getting there by sending less. They’re smart and they’re learning how to send more.

These marketers are like the successful farmers in the classic illustration of diminishing returns. Email is the fertilizer that boosts their per-acre yield: their revenue. Up to a point, yield increases on pace with additional fertilizer -- but after reaching the optimum amount, the boost from adding fertilizer starts to decrease. Eventually there’s nothing to be gained from adding more.

The email marketers that ramp up sending volumes without sacrificing inbox placement are the best at finding that optimum point, and they find it by testing. Here’s how to follow their lead:

1. Segment your audience by engagement. The most-engaged -- the subscribers that read your messages, rarely ignore them, often forward them, etc. -- typically represent your best opportunity to test higher volumes. Moderately engaged subscribers may represent a lesser, but still valuable opportunity. Weak engagement, on the other hand, tends to coincide with poor response to higher sending volumes.

2. Know your key competitors’ sending frequencies, especially to the subscribers you share, and compare your levels of engagement. Test increases with caution if high-frequency senders are failing to engage their subscribers, but don’t automatically assume that your program can’t send more mail because theirs isn’t working. Better content and stronger relationships may allow you to increase volumes when others can’t.

3. Test different types of messages separately. Your subscribers may want more newsletters or updates from you even if they have little appetite for more offers. Monitoring competitive campaigns including those outside your immediate industry can guide your testing here, too.

4. Take it slow. When you’ve identified opportunities to send more mail, ramp up gradually. In addition to making it easier for mailbox providers to distinguish you from spammers, avoiding abrupt or jarring shifts in message cadence will help reduce complaints or engagement drop-offs.

5. React fast. Monitor reputation and engagement metrics for early indications of tolerance thresholds and respond quickly to declines.

6. Keep testing. Changes in offline behavior, site activity, purchase patterns, or email engagement signal opportunities to respond by sending more or different messages.

Just as in the farming analogy, these approaches to identifying optimum sending volumes are disciplined, measureable, and replicable. They’re more science than art, but their ultimate goal is far more human than methodically finding the point of diminishing returns: It’s finding how much your subscribers want to hear from you, which ones want to hear more, and what they want more of. It’s as much a customer satisfaction initiative as a business growth initiative.

Of course there’s one important distinction that makes a farmer’s search for the point of diminishing returns less applicable than an email marketer’s: You can over-fertilize a field by an absurd amount before yields actually decrease. In email marketing, yields decrease in a hurry as excess volume reduces subscriber engagement and mailbox providers react by filtering or blocking messages. In email marketing, excess "fertilizer" gets called something else.