It’s been a nagging question about direct marketing for years now: To what degree does personalizing a mass marketing program improve audience engagement and action?

Back in the old days, personalization was difficult to pull off, because the limitations of printing meant that the way people’s names were inserted into letters looked awkward and even jarring – different typeface, different ink concentration, etc.

Instead of creating a positive impact that suggested a personal relationship with the recipient, the effect was often just the opposite: the ill-fitting interpolations screaming “mass mailer.”

Today, with so many marketers targeting consumers electronically versus via postal mail, personalization has become a common technique used for the same purpose: to draw the reader’s attention by making the e-communiqué “unique” to him or her. Plus, it’s much easier to accomplish.

But how is this working out in the digital age? The latest e-mail marketing metrics report from email marketing and newsletter services provider MailerMailer, LLC, issued in July 2011, uses data compiled from more than 977 million opt-in e-mail newsletters in a sampling of over 1,600 customers. It found that adding the recipient’s first or last name to the subject line of an e-mail often generates negative, not positive results.

On the other hand, personalization within the message portion of the e-mail makes it a tad more likely to lead the recipient to interact with the message.

Here are the open rates MailerMailer found based on the degree of personalization:

 Subject line personalized: 4.1% open rate
 Both subject line and message personalized: 4.6% open rate
 Message personalized: 12.6% open rate
 No personalization at all: 11.4% open rate

[MailerMailer claims that personalized subject lines perform less favorably because this has been such a common tactic used by spammers in recent years. I claims the method has been so overused, recipients now associate all such e-mails as spam.]

And what about clickthrough rates — the more important metric? MailerMailer’s findings track neatly with the open rate trends, as follows:

 Subject line personalized: 0.8% clickthrough rate
 Both subject line and message personalized: 1.1% clickthrough rate
 Message personalized: 3.0% clickthrough rate
 No personalization at all: 3.0% clickthrough rate

So another thing the MailerMailer report is telling us is that the effort to personalize e-mails may not be worth it in the end. It’s true that a slightly higher open rate may occur with personalized message content … but the clickthrough rate, which is the more important metric, doesn’t budge at all with personalization versus without it.

So it would seem that personalizing e-mails isn’t something that’s going to “make or break” your direct marketing campaign’s success rate. Better to focus on the other classic success factors: the message, the offer, and the target recipients list. You know … just like always.