Keeping Your Email List Clean: Why Prevention is Better Than Cure (Part 1)

Some of the most common questions that I get asked relate to keeping email lists clean, commonly known as list hygiene.

In this blog post, I’ll explain how list hygiene can impact your sender reputation and I’ll also explain the different types of “bad” email addresses that you should avoid sending emails to. In the next blog post, I’ll then explain how to keep your email list clean, describe the most common methods, and explain the pros and cons of each.

Keeping your email list clean is incredibly important. If you don’t do it, it can have a huge impact on your sending reputation and ultimately cause your emails to end up in the spam folder.

The RACE Model:

Firstly, I’ll recap on the four pillars of deliverability that can all affect whether or not the emails that you send will reach the inbox, or whether they’ll be confined to the spam folder. They spell out the word RACE, which stands for:

  • Reputation
  • Authentication
  • Content
  • Engagement

Recap on Reputation:

In general, reputation plays a big part on whether your email will be delivered to the inbox. If you send emails to “bad” addresses, it will very quickly drag your reputation down and you’ll find that more of your emails end up in the spam folder.

What counts as a “bad” address?

There are different types of “bad” addresses and I’ll explain some of them here:

Spam traps

These are the worst possible types of email addresses. You should never send emails to an address that you believe to be a spam trap. Spam trap addresses are set up to catch different types of email sending malpractice such as “scraping” email addresses from the Internet, or continuing to send emails to addresses that no longer work.

If you inadvertently send an email to a spam trap, you can be almost certain that your sending reputation will take a hit. 

Bot addresses

Fortunately, bot addresses aren’t that common, but if the email address of a bot ends up on your email list, it’s not very useful. A bot (abbreviation for robot) address is an email address that gets “read” by a computer. Typically an email sent to a bot address will always appear to be opened and clicked and it’s possible that they could do other more harmful things with your email, such as forwarding it on to other people who didn’t request it.

Malicious opt-ins

This type of bad address is notoriously difficult to protect against. The simplest example is a real person filling out one of your opt-in forms with someone else’s email address where that person has not given their permission for you to send them emails. The more common example is where  an automated “bot” will attack one or more of your opt-in forms and sign up lots of email addresses from real people, even though none of them have given you permission to email them.

It’s often difficult to differentiate between a genuine opt-in versus a malicious one; fortunately a lot of the spam bots that do this kind of thing use random strings of letters and numbers as the person’s name, so you can sometimes visually spot these as they come in.

If malicious opt-ins do slip through the net and you send emails to those addresses, there’s a very high risk indeed that those people will click the “spam” button when they receive your email. This is to be expected, because they obviously didn’t request your content in the first place, but if it happens more than a handful of times then it’s very likely that your sending reputation is going to be badly damaged.

Invalid email addresses

These are addresses where you’d expect to see an error when sending to them, and can take the form of:

  • email addresses that were previously in use but no longer exist
  • email addresses that look correct but have just never been used (they most commonly end up on your email list because somebody misspelled their email address when they completed a form)
  • email addresses where there is a syntax error, meaning that the email address would never work (for example because the @ sign is missing, or there is no dot in the domain name)

Sending an email to an invalid address might not hurt your sending reputation in the eyes of the mailbox providers such as Google, Microsoft and Yahoo, but it can hurt your sending reputation in the eyes of your email marketing provider, and you should never send emails to invalid addresses. 

As an example, Amazon’s SES (Simple Email Service) recommends that you should maintain a bounce rate below 2% and will place your account under review if your bounce rate exceeds 5%.

Role addresses

Where an email address is related to a particular activity rather than a particular person, this is considered a “role account”. Examples could be email addresses that start with “info@” or “sales@”. In many cases, there is a risk that these addresses are actually distribution lists that get forwarded to more than one person, in which case you’d expect a much higher spam complaint rate than normal. In the vast majority of cases, it’s best to not send emails to role addresses.

“Catch All” addresses

Most mailbox providers will reject emails where the name before the @ sign isn’t linked to a valid, active mailbox. This allows you to easily remove people from your list where the address doesn’t exist. However, some email domains are set up where any name before the @ sign will be accepted, whether it exists or not. In some cases, everything is forwarded to one mailbox; in others, the emails are just silently rejected.

Either way, a “catch all” address isn’t ideal because there’s a greater chance than normal that emails won’t make it to a real human being, and might therefore contribute to lower open rates, lower engagement and, hence, lower sending reputation.

So, while it’s not necessarily a bad thing to send emails to “catch all” addresses, it can still pose a risk to your sending reputation and it’s vital to make sure that you’re removing email addresses from your list if they haven’t engaged within a reasonable time, normally 90 days.

“Seed” addresses

Seed addresses generally belong to an organisation that monitors email performance or email compliance. Companies such as Validity (formerly ReturnPath), GlockApps and others use seed addresses to monitor whether or not emails were delivered to the inbox and to get a measure of email volumes sent from individual domains.

As long as you’re not sending malicious emails, it doesn’t harm your reputation if you mail to seed addresses. But if you don’t want those organisations to know what you’re sending, you might prefer to remove those addresses.

Disposable addresses

Disposable email addresses are temporary ones that have a very short lifespan – often just 10 minutes or maybe an hour. They’re often used by people who want to opt in for some content without revealing their real email address and without wishing to continue receiving follow-up emails. Sending emails to disposable email addresses doesn’t harm your reputation as such, but you can be sure that the address will expire soon after and any attempt to send an email to that address in the future will then fail.

Any other address that you don’t have permission to contact

Although this doesn’t technically count as a “bad” email address, there’s an important thing to bear in mind: Any email address that you don’t have explicit permission to contact should be considered a bad email

Here’s why. If someone hasn’t given you explicit permission to send them an email, the chances of them clicking the “this is spam” button on any email you send them is hundreds of times higher than if they’ve given you permission. 

So remember, only send emails to people who have opted in to your mailing list by filling out a form, or specifically told you that it’s ok to mail them. Adding their email address because you’re connected on LinkedIn just doesn’t cut it.

The impact of sending emails to “bad” addresses

Some types of “bad” address don’t really hurt your reputation that badly. But if you repeatedly send emails to spam traps, malicious opt-ins or addresses that you’ve added to your list without explicit permission, you’re going to end up hurting your reputation very quickly indeed, and that’ll mean the emails you send become much more likely to end up in the spam folder.

Similarly, every email marketing provider will tolerate a reasonably small percentage of invalid emails that cause bounces when you send to them. But again, if that percentage gets too high, you could end up with a warning to clean up your act.

How to avoid sending to “bad” addresses

There are several different ways of avoiding sending to “bad” addresses including opt-in validation, email address verification and list scrubbing. 

I’ll explain these in more detail in the next blog post; in the meantime if you’re worried that you’ve got a lot of spam traps and other “bad” email addresses on your mailing list, why not check out my free Deliverability Dashboard tool which includes an easy-to-use integration with Klean13, one of the industry’s best list scrubbing tools.