“Be sure to white list this email address…”

Today a lesson about blindly following the crowd:

You've no doubt seen a welcome email before where the sender told you, “Be sure to white list this email address so you don't miss any of our messages!”

A lot of people do this.

The premise is that getting a percentage of your subscribers to white list you means more emails getting delivered, opened and read—a higher quality, more engaged list, in other words.

But does it actually work?

Recently I tried an A/B test to find out.

Here's what I did:

For the test group, I added a P.S. to the welcome email, offering some bonus content if the new subscriber would add the sender's address to their address book, then hit reply and let me know.

Over the next month, 1,078 new subscribers received the white list request, and 1,046 subscribers did not.

4.1% of the test group subscribers replied for the bonus content.

(I was actually pretty surprised how high the participation was. Without an incentive I suspect less than 1% of people actually follow through on a white listing request.)

What impact did this have on subscriber engagement?

According to the tracking in Drip, the group that had white listed me showed 5% LESS engagement (opens and clicks) than the control group.

I have some ideas about this result, but I'd be curious to hear your thoughts first.

What is going on here?