(Business 2.0) – When Gap, Hewlett-Packard, Tower Records, and Verizon e-mail those ubiquitous customer-outreach dispatches, a funny thing happens: They get read.

A key reason is that all those companies are clients of Digital Impact, a San Mateo, Calif., outsourcer specializing in e-mail marketing. The six-year-old firm serves an impressive list of Fortune 1,000 clients and, more to the point, boasts click-through rates that run upwards of 15 percent, or nearly thrice the industry average. Any company looking to sidle up closer to customers could do worse than take a screenpage from Digital Impact's proven recipe (as we did with the Tower Records "jazz newsletter" annotated here).

The secret sauce is personalization. Once a user agrees to receive e-mails from the likes of HP or Gap, Digital Impact's software starts to log that person's online purchasing habits. Then, with each e-mail contact, the company probes for insights into personal interests to better tailor subsequent missives. Add a dose of good timing--Digital Impact contacts a user only when the client has something to say about a concert or sale--and you've got the difference between serving your customers spam and inviting them to a steak dinner. --NANCY EINHART AND BRIDGET FINN

Don't Summon the Spam Police

Grabbers like "Discount!" and "Free!" trigger spam content filters, so Digital Impact exercises salesmanship with some restraint.

From: Tower.com Subject: In Jazz: Save 25%, catch Larry's latest reviews & more! Date: Summer 2003

Study the Customer

To better tailor the messages, Digital Impact tracks a reader's every click. Such scrutiny pays off: Tower's genre-based campaigns boast an impressive 16 percent click-through rate.

Follow Up

The outsourcer follows Tower's catalog drops days later with e-mails featuring special offers. The efforts have helped goose a segment of Tower's online business by 76 percent.

Mind the Layout

Digital Impact sees its e-mails as newspaper front pages: The most important content goes "above the fold" to grab the reader's attention.

Build Goodwill

Everyone wants advice from an experienced ear. Digital Impact urges its clients to cram insights and tips into each newsletter.

Give 'Em What They Want

Digital Impact constantly seeks details about customer preferences. Enjoy R&B? Prefer text e-mail? Specialized content helped Tower lower its unsubscribe rate below 0.5 percent.