Doing process audits may seem like a waste of time. After all, you probably won’t find anything major and there are lots of other things on your to-do list. But then again, you might indeed find something major and be super thankful you took the time to investigate.

Last month, I released the Email Opt-In Audit Imperative infographic that details research showing that more than a quarter of email signups that occur via the homepages of major B2C brands are not honored or experience significant delays in being honored. Since your most valuable email subscribers sign up via your website, these results are worrisome. And your homepage is just one of probably more than a dozen ways that subscribers join your list, so there’s potential for many more process breakdowns that could be slowing list growth.

Exhibit A: Just a few weeks ago I received an email from Lands’ End with a subject line saying that it’s “Been too long!” Typically that’s the kind of language you’d see in a win-back email where a subscriber hasn’t engaged in a long time, but in this case this was the first email Lands’ End had sent since their welcome email more than 6 months earlier.

It appears that they uncovered a glitch in their signup process whereas email addresses weren’t getting added to the active list properly, and this email was their way of rebooting the email relationship. I don’t know how long the glitch persisted or how many subscribers were affected, but I suspect there was a very significant opportunity cost associated with it.

Exhibit B: Lowe’s experienced something very similar a few years ago. In January of 2011, I received an email from them with the subject line “Sorry we are a little late, but great values like these are worth waiting for.‏” The account where I received this email was used to subscribe to Lowe’s emails more than two years earlier, and I hadn’t received any emails from them until this one.

Exhibit C (added 10/16): Northern Tool had a nearly identical experience as Lands’ End. It also took them more than 6 months to honor my opt-in. Their first email went much lighter on acknowledging the problem and apologizing. They choose to only mention it briefly in the preheader, but they did add a prominent unsubscribe link, wisely recognizing that after such a long delay that some folks might not be interested anymore.

Kudos to these brands for discovering these problems, taking actions to fix them, and reaching out to affected subscribers. My experience has been that the vast majority of these signup breakdowns go undetected for years or get fixed unknowingly when updating or upgrading systems.

Make sure that you’re not missing out on valuable list growth by auditing all your email acquisition sources—and if you can do it ahead of the holiday season, then all the better.

There are now many more ways to grow your list of subscribers than ever before, but the downside to that is that all those additional sources of subscribers have created a lot more complexity, which can make it difficult to see how each is performing and to see problems when they arise.

In a “tip of the iceberg” research study, we tested the homepage email signup process of more than 160 B2C brands, including retailers, restaurants, manufacturers, travel and hospitality, and nonprofits. For most brands, this is their best source of high-quality subscribers, so the breakdowns and delays that we discovered there are likely an indication of more troubles beneath the surface—and untapped opportunities to improve list growth.