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10 Steps to Keep Bad Email Addresses Out of Your Database

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by: Loren McDonald (@LorenMcDonald)
12 March 2014

If you don't think you have a problem with bad addresses in your database, think again.

As with most email marketing issues, your susceptibility depends on many factors: ease of subscription, acquisition strategy and tactics, and (perhaps surprisingly) your mobile friendliness.

"We've seen databases where invalid addresses make up just a couple percent to those where it's over 70 percent," says Austin Bliss of FreshAddress. "It's not just undeliverable addresses. Many also come from bots that you shouldn't be sending to even though they're technically deliverable addresses."

As I explained in my previous blog post on this topic ("Defend Your Database Against the Bad-Address Bots"), bots are automated computer programs that search the Internet for specific forms in order to register for or capture a reward.

Start by Reducing Opt-In Mistakes

Standard list hygiene should suppress undeliverable addresses. However, that's only part of the solution.

"You have to find a way to allow people to correct their mistakes," says Matt McKee of BriteVerify.

Making your opt-in process more mobile-friendly can reduce typing errors and increase your mobile opt-ins as well as those from desktop users.

"The average invalid rate at point of collection is 6.7 percent, and nearly 70 percent of the time, people will correct their email address when prompted," says Craig Swerdloff of LeadSpend. "So, if I were to assume that the 70 percent had legitimately made a typo when filling in their email addresses, I could estimate that nearly 5 percent of email addresses are mistyped by accident. The other 2 percent are either the result of bots or people intentionally mistyping their email address."

These five steps can help you increase address accuracy at the start:

1. Move your opt-in invitation and address field higher up on your pages to make it more visible to all viewers. Too many websites hide the opt-in at the bottom of the page under the live content. The longer customers have to look for it, the less time they’ll give to make sure they’re filling it out accurately.

2. Add social sign-in to give subscribers a one-tap option.

3. Add a confirmation screen that repeats the address the user typed in and offers an edit function to fix mistakes.

4. Add real-time verification that detects typing mistakes and either suggests changes or opens a second field to retype the address correctly.

5. Reduce the complexity of your opt-in form and redesign to be more mobile-friendly.

Move to Real-time Verification/Validation

Making your opt-in process more mistake-proof won't stop bots from hijacking your promotions.

The tools many marketers use now (double opt-in, CAPTCHA and other process-interrupters) are usually applied to every registration request, not just the sketchy-looking ones. This reduces your legitimate opt-ins.

When you move to a system that incorporates several approaches to the problem, you can more accurately separate legitimate registrations from those that look like bots, spoofs or mistakes.

Done in real time, you can verify an address before submission, which, in turn, keeps more bad addresses out of your database, increases deliverability and keeps you cool with the ISPs.

The five steps listed below are part of a real-time validation process and can be programmed via plug-in tools, business rules written into your email acceptance protocol, or combined through a third-party validation process.

1. Verify address and offer self-correction.

Your registration system would check the domain name in the address (the part after the "@" symbol) against a list of registered domain names and either suggest alternatives or ask the user to try again if the domain name doesn't match up.

A real-time validation service can also ping the user's email address to make sure a corresponding valid mailbox exists before submission.

2. Deny "role" email addresses, potential spam traps and disposable or other problem addresses.

Role accounts are usually tied to jobs rather than individual people and are deliverable but worthless. Examples: "," "Support@" or "Info@." You can also match the address against your own database of spam complainers, honeypots, disposables, etc.

3. Throttle addresses from specific domains.

A sudden influx of opt-ins from a single domain within a set time period can indicate that a bot is trying to milk your new promotion with bogus registrations. To combat this, limit registrations from a single domain in a specific time period, based on what's normal for your business, and add a CAPTCHA or opt-in confirmation request to other requests from that domain.

A company that does business in only one country, for example, could throttle or deny requests from foreign IPs or domains.

4. Add confirmation requests or CAPTCHA forms to suspicious-looking entries.

Apply this on registrations from throttled or frequently spoofed domains like or As a variant, add a secondary form that only a bot would see, and then suppress any registration that had data in that hidden form.

By being selective about where you apply these forms, you don't annoy your legitimate (or legitimate-looking) customers.

5. Send a confirmation email with an unsubscribe link.

"This is a best practice, but it's also a way to weed out accidental opt-ins or those that are jokes or malicious," says Bliss. "We advise people to track unsubscribes from these messages differently from later messaging sequences."

As you can see, keeping invalid and worthless addresses out of your database takes multiple steps and a little time and thought, but the payback is immediate and immense.

Many thanks to my panel of experts for sharing their time and technical knowledge: Matt McKee of BriteVerify, Austin Bliss of FreshAddress and Craig Swerdloff of LeadSpend.

If you have any questions, or you'd like to comment on your specific issues in address quality, feel free to add your remarks below. Sorry, no bots allowed.

Related Resources:

1) Blog: “Defend Your Database Against the Bad-Address Bots

2) Ebook: “15 Post-Purchase Emails That Build Loyalty and Drive Revenue

3) White Paper: “List Hygiene Guide


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