According to the "trickle-down" theory of economics, wealth inevitably works its way down from the rich into the pockets of the poor.

A corollary to that is the trickle-down theory of technology. This postulates that while the use of new technology tends to be limited initially to an affluent few, it eventually finds its way down to the rest of us. A prime example is e-mail, which has become as indispensable a business tool as the telephone, the postal service or the fax machine.

In fact, e-mail has become so widespread in the last decade, that the use of e-mail marketing is growing while direct "snail mail" marketing is on the decline.

In a report published earlier this year, GartnerG2 —the Stamford, Conn.-based research branch of Gartner, Inc.— predicted that e-mail advertising revenues will reach $1.26 billion this year, up from $948 million in 2001. By 2005, e-mail advertising revenue is expected to total $1.5 billion.

As e-mail marketing is burgeoning, direct mail has reached its peak thanks to rising postal and printing costs and increasing "junk mail" legislation enacted by federal and state lawmakers.

The Gartner report notes that compared to direct mail, e-mail marketing campaigns have proven to be more efficient and their success more easily measured. On average, it takes four to six weeks to complete a direct mail campaign vs. seven to 10 business days for an e-mail campaign. And responses to direct mail take an average of three to six weeks, while responses to e-mail take an average of three days.

In addition, e-mail campaigns are significantly less expensive to execute than traditional direct mail campaigns. E-mail costs range from $5 to $7 per thousand, while direct mail costs range from $500 to $700 per thousand.

GartnerG2 warns that permission-based and opt-in marketing strategies are critical to higher e-mail response rates. In general, response rates from direct mail are the same as e-mail, hovering at one percent. However, on permission-based e-mail the response rate rises to six to eight percent.

Among Gartner's recommendations for using e-mail marketing:

• Use personalization to address your customers, making sure to acknowledge your relationship with them.
• Always allow your customers and prospects to provide feedback. Then acknowledge and use it to better your next communication.
• Limit the number of e-mails to no more than three per month for business audiences.

E-mail marketing experts stress that a successful marketing campaign should also follow these rules:

• Subject lines have to be genuine, accurately reflecting the content of the e-mail.
• Every e-mail must include options for the reader to opt-out of further commercial e-mails.
• Senders should clearly identify themselves in the return address.
• Customers should be allowed to block the sale, exchange or rental of their addresses.
• Your e-mail should always provide offline contact information including a street address, city, state, zip code and telephone number for inquiries and complaints.

But you don't need to "opt in" to send your comments and/or suggestions to harper.d@att.net.