Assuming too much about your relationship with your newsletter subscribers can get you into trouble. Underscore Marketing's president explains how to sidestep problems.

The temptation is always there. You grow a healthy list of interested newsletter recipients over time and have captured a significant percentage of the market. You've managed bounce rates and churn as well as you can, and it becomes obvious that the way to grow your newsletter business is by expanding your content offering, rather than continuing to try and acquire subscribers for your existing newsletter. But should you to force-subscribe your existing subscribers to the new content?

From a business perspective, it makes sense to force-subscribe, or at least to do so on a trial basis. Subscribers who don't like the content can always opt out of the incremental offering. And it's much easier to build a subscription base on an opt-out basis than to build one from scratch.

Who can resist the temptation to build quickly at the expense of a few angry subscribers?

The problem lurking here is not simply that a few subscribers will get angry enough at the notion of being force-subscribed to opt out and end your relationship. Consider the cumulative effect of doing this several times. After all, what will happen after you've grown the new content offering and it's time to expand again?

Newsletter subscribers are less tolerant than ever of email marketers who abuse their relationship by sending content or offers the subscriber never asked for, or who deliver emails that are otherwise out of line with the expectations spelled out at signup.

Attribute it to a combination of time constraints and the ability to get content in new ways that give the recipient more control (think RSS feeds, search, email alerts).

There's also a hard and fast limit to the amount of time a subscriber can spend with each content offering before throwing up their hands and saying, "Enough!"

I was thinking about this last week as I unsubscribed from newsletters I've read for years. Years ago, I signed up for one email newsletter to get more insight into what my traditional media brethren were up to. Over time, the content provider must have assumed that if I was interested in what I was already getting from them, I must also be interested in all the other newsletters they published to cover other aspects of the marketing business. Most of this stuff ended up getting trashed without being read. Eventually, though, this content provider swamped my inbox with enough content to make me feel deluged. Call it a housecleaning of sorts -- I ended up ditching everything.

Over time, the newsletter I had come to rely on was replaced by targeted RSS feeds, some Google Alerts I had set up and news aggregation at a handful of social networking sites. It was less of a "must read" because I was getting the news elsewhere. The decision to unsubscribe was a done deal once it became obvious that the relationship with the content provider was one that would continue to be abused.

Email has a lot more to compete with these days than it ever did. More importantly, the new media that are supplanting email as a content delivery mechanism place more control over the flow of content and advertising in the hands of the end user. It's thus obvious that email marketers need to watch their step and avoid giving subscribers a reason to bail.

Tom Hespos is the president of Underscore Marketing and blogs at Hespos.com. Read full bio.