eMarketer reports that companies favor email, and look to it to promote viral marketing.

Nearly all interactive marketers send email. According to a recent Forrester Research report, "Interactive Marketing Channels to Watch in 2006," 93 percent of the 259 respondents cited email as a marketing channel they use or plan to use to reach consumers. At 13 percentage points more than even highly touted search marketing, that makes email as universal as a marketing method can be.

Email is extremely important in the B2B realm, too. This was indicated by the 60 percent of marketing executives at U.S.-based manufacturing companies who said they planned to increase email usage in 2006 (12 percentage points over search engine marketing) in an April 2006 survey by SVM E-Business Solutions.

Increasingly, to make the most of their existing opt-in email lists and to grow those lists even further, companies look to blend word of mouth into their email marketing mix.

While much word of mouth among consumers takes place offline, in-person, or on the telephone, the internet is an integral part of both their conversations and marketers' attempts to join these conversions. According to recent research from the Keller Fay Group, a company co-founded by Ed Keller, the former chief executive officer of Roper ASW and co-author of the book "The Influentials: One American in Ten Tells the Other Nine How to Vote, Where to Eat, and What to Buy," the internet is the main medium U.S. consumers most frequently reference in their brand-related word of mouth.

David Hallerman is a senior analyst at eMarketer. This article is drawn from the recent eMarketer report E-Mail and Word-of-Mouth: Connect with Your Best Customers. Contact eMarketer directly.