There are plenty of reasons for email marketers to pay attention to their unsubscribes—some of them obvious, others less so.

Of course, among the actions our subscribers may take—opening email, clicking through links to our Web sites, responding with feedback—a request to stop receiving email can certainly be ranked among the least desirable.

But if we read a bit between the lines, we might find some value by learning both to reduce the number of unsubscribes from our campaigns and to better engage those who stay with us.

Top 5 Reasons People Opt Out of Email Campaigns

Over the last decade, I've combed through countless feedback messages from marketing campaigns, and the following five reasons for opting out appear time and time again:

1. Email Frequency

Like us, our subscribers receive lots of email. If they come to feel that they're receiving too much, they may become overwhelmed and decide that none is the better alternative to an unmanageable amount.

This decision to declare "email bankruptcy" means that subscribers mass-unsubscribe from several campaigns at once when they hit a tipping point.

We certainly can't help how many emails our subscribers are getting from others, but if we're sending too many ourselves, we're more likely to be singled out for unsubscribing, or bunched in with and purged along with other culprits.

On the other hand, if we send email only once in a blue moon, subscribers may very well have forgotten who we are or that they'd requested information from us in the first place. Sending too few emails also quite often leads to unsubscribes.

2. Quality or Relevancy of Content

In email, you can't separate quality from relevancy.

It's clear that people don't want to receive email for sake of filling their inboxes. They want value—messages that engage them with compelling content that's related to what they originally expressed interested in receiving from us.

If email campaigns stray from providing relevant information or fail to fill emails with anything more than sales pitches, the rate of unsubscribes tends to grow.

3. Change in Relationship Between Sender and Subscriber

For better or worse, our relationships with subscribers of our email campaigns (just as with relationships outside of email) won't be the same forever.

If our marketing is successful, prospects become customers. A purchaser of one product may then go on to buy others.

On the other hand, subscribers may cancel a service billed on a recurring basis, or they may return a product they purchased. Quite possibly, they could shift interest away from our industry altogether.

Any of the above could make obsolete the information that we're emailing to recipients, causing them to unsubscribe from a campaign—hopefully while signing up for another.

4. Personal Reasons Not Related to Email Content or Frequency

Quite often, in comments left by subscribers on their way out, I'll see messages such as "I'll be on vacation for the next two months and won't be checking my email" or "I'm putting all business on hold while tending to a family illness."

Our subscribers are people, and things we can't control will inevitably come up in their lives that may cause them to rightly choose to stop receiving our emails for at least a short period of time.

Fortunately, many of these people will come back when the time is right for them.

5. Email Address or Subscription Method Change

Just as people move and change their physical locations and postal addresses, email subscribers sometimes change email addresses or want to receive our email at other addresses.

Often, they'll use a feature for changing their current subscription's options. Other times, they'll unsubscribe then return to an opt-in form and sign up with another email address.

If another way of syndicating information, such as RSS, is available for readers, it's not uncommon for them to decide to receive our information through that alternative channel and unsubscribe from receiving email.

Let Some Subscribers Go

It's easy to feel dejected about losing subscribers who opt out. After all, these people have rejected our email... and no one likes rejection.

So does the solution lie in attempting to reduce our unsubscribes to zero or as close to it as possible? I'm afraid not.

It should be clear by now that there are some unsubscribes that we simply can't avoid. Some people just aren't interested in what we have to say or they have other, competing priorities; we have to learn to let them go.

Besides, if we spend our time and resources on trying to please everybody, we just might find ourselves pleasing nobody.

Unsubscribes Will Teach Us Something, If We Listen

And yet, there's no need to feel defeated. Remember, some of the numbers we see may involve temporary situations that will result in a continued subscription at a later point, while others leave us with a new or different way to continue marketing to readers.

Perhaps more importantly, the feedback we receive from people removing themselves from our lists can shed some important light on areas we might make adjustments to in order to improve our campaigns.

We might test a weekly newsletter against a monthly one to see what resonates better with subscribers. Or, perhaps, we find motivation to double our efforts for giving subscribers relevant content they connect with.

Remember, if something is on the mind of a few, it very well may be on the minds of many. If we take cues from the feedback we receive and understand what causes a number of people to exit, we also learn something valuable about our subscribers who stick around—the ones we will continue to profit from.