Email address appending has been in use since the late '90s, and if my inbox is any gauge there's a rebound in its use.

I've recently received emails from catalogers, publishers, and major marketers with which I've done business in the past, asking permission to send me emails. And that's the first key to successful appending, since it is meant only for existing relationships.

Most marketers have email addresses for less than half their customers and prospects. If this is the case for your company, it might make sense to explore email appending.

Let's first look at the process, and then we'll examine how one publisher implemented its communication plan.

How the Process Works

Many companies offer email appending services. The larger services have 70-90 million records with name, address information, and email address. You provide them with names and addresses of customers or prospects, and they match your file against their database.

You should use fairly tight match criteria and match on an individual-name—not on a last-name or household—level.

Match rates for business-to-business will be in the 10-15 percent range and consumer marketers can expect 25-30 percent.

Some appending companies will send the first email for you, and others will simply provide you with all the matches for you to send. The first email is called the "permission pass."

You'll want to wait at least a week after the permission pass to collect any bounces or opt-outs. Typically, you'll see low opt-outs, normally in the two-percent range.

The Permission Pass

There are some mandatory elements that should be included in this email. You should explain the existing relationship, tell recipients you would like to now communicate with them via email, and give them a clear opportunity to opt out.

Many e-commerce marketers will also include a special offer in the permission pass email.

I mentioned that I wanted to use a publisher as an example. I'm a former subscriber of its publication. Its permission pass email used the simple but strong subject line "[Publication] Requests Your Permission." That's a great start. As the recipient I immediately recognized the publication.

The publisher's email was all text, although it used HTML-lite and the message was easy to read and had some style. I give the message negative points for not including any graphics such, as the publication's logo.

The first paragraph got right to the point. "As a former [Publication] reader, we respect your time and value your business. Occasionally we would like to send you email communications containing special offers & exclusive invitations from [Publisher]."

The rest of the email included a chance to opt out and a toll-free number to contact customer service. The online marketing manager signed it. I found it refreshing to receive an email signed by a person.

The First Regular Email

It is likely that some recipients did not open and read the initial permission pass. A mistake that many marketers make is to add all the names to their regular sending schedule. Those who did not read the message may wonder why they now receive newsletters and other offers.

Our publisher did not make this mistake. Above the header, in small type, its first email said: "You received this email because you are signed up to receive information from [Publication]." And, the subject line also alluded to my relationship: "Welcome Back Rate for Former [Publication] Subscribers—26 issues for $20!"

Since I'm an expired subscriber, it makes sense to try to convince me to re-subscribe. The message was in HTML, included prominent placement of a sample magazine cover, and had two calls-to-action in red to "Try 4 Risk Free Issues Now."

The Next Six Emails

I received about two emails a week from our publisher. Each one has information above the header in small type about why I am receiving their communications.

Here's a summary of the emails received with the subject line and comments:

1. Welcome Back Rate for Former [Publication] Subscribers—just $.77 an issue. The email was sticking to the company's mission to get me to re-subscribe. The creative was different from my first email's.
2. 2008 Leadership Conference Invitation. This was a third-party email from one of the company's advertisers. At the top, the message in small type explained: "You received this email because you are signed up for special offers from [Publication] advertisers." I was surprised that I was receiving other offers, and went back to review the initial language in the permission pass. It did mention special offers and exclusive invitations. I think the language could have been clearer, though.
3. Welcome Back to [Publication]! Get 4 Free Trial Issues. The creative was the same as my first email's; only the subject line had been slightly tweaked.
4. "Welcome Back Rate for Former [Publication] Subscribers—26 issues for $20!" The creative was the same as email 2, with subject line changes.
5. GREENER GADGETS CONFERENCE—February 1st 2008, New York City. This was another third-party advertising email. The use of caps in the subject line is not a best practice.
6. Special offer for former [Publication] subscribers: 4 Risk-Free Issues. This email featured a new creative presentation, and the salutation in the email was personalized with my first and last name.

All in all, our publisher did a good job with the permission pass and subsequent emails. I liked the use of varied creative presentations and small changes to the subject line for the main offer. I would have preferred a clearer explanation that I would receive advertising emails. My only other comment is that the publisher cross-promote its site, e-newsletters, books, and other offerings rather than just focusing on re-subscription.