Marketers are continually looking for ways to tweak e-mail campaigns to improve their success. From direct mail tradition, we know the “list” and the “offer” are highly important success factors, followed by the creativity and appearance of the promotional piece itself.

But what’s different about e-mail marketing campaigns? Doesn’t a compelling and informative “Subject” line in the inbox also have a lot to do with their success?

Well … yes. But in field research conducted recently by Epsilon, a leading direct marketing agency and consulting firm that queried more than 600 North American respondents, the findings revealed that there’s another factor that is far more important than the “Subject” line. It’s the “From” line on the e-mail.

In fact, nearly 70% of the respondents cited the “From” line as the single most important factor determining whether or not they’ll open an e-mail message. And this figure is up from 60% in Epsilon’s 2002 survey, so the trend is clear.

By contrast, the “Subject” line is the most important factor for only about a quarter of the respondents.

What this means is that people are looking to see if they know (and trust) the sender before they do anything else … even before reading the subject line of the e-mail. Thus, a poorly performing e-mail campaign might have less to do with the campaign’s specific marketing elements than it does with the sender’s familiarity and reputation.

With groaning e-mail inboxes, is it any wonder that people are inclined to eyeball the “From” column, quickly scanning for the (few) e-mails they’ll open as opposed to the scads of other messages they’ll delete without a second thought?

In short, the “From” line offers comfort. It’s the familiarity of people they know … companies with which they have a relationship … brands that they trust.

That’s also why it’s so important for marketers to send “welcome” or “thank you” e-mails to new registrants without delay. Why risk having someone forget they signed up, and then hitting the unsubscribe button (or worse, lodging a spam complaint) when your messages hit their inbox later? That’s snatching defeat from the jaws of victory.