List Hygiene

Keeping your company’s email list accurate and up to date is a continual commitment. It takes some work. The following sections discuss the main steps in getting the most out of your curated email list.

Avoid Auto‐Subscribe

Every subscriber on your list should remember asking to be on your list. When you capture an email address in conversation, from a business card, or even from a transaction, it is not an implicit subscription to your newsletter or promotional emails. Some marketers cave in to temptation and automatically add these to the campaign list. A better practice is to send an invitation to these people, asking them to expressly sign up for your campaigns or newsletter. If they don’t respond, then don’t add them to the list.

Scale Down Inactive Subscribers

Make it your goal to keep only engaged subscribers on your list: those who interact with your messages or content. How long until a subscriber is considered inactive? It’ll be different for each entity, but a good starting point is twice your normal sales cycle time.

Responsible email marketers regularly clean lists, removing inactive subscribers in order to maintain high deliverability. Some more experienced marketers simply delete inactive users based on a time‐without‐interaction. Some put inactive subscribers on a less frequent schedule.

Another effective practice is to send farewell messages to inactive subscribers prompting for a resubscribe confirmation. Then remove those who do not confirm a desire to remain subscribed. This may seem counterintuitive to marketers who want to maintain a large list. It’s a painful process for some of us! We think, “What if they don’t see my reconfirmation message?” But know that the reputation of your domain or sending server is at risk if your emails are being sent to recipients who ignore them or fail to interact. Conversely, it stands to reason that, if a high majority of your recipients are observed to open, click, or “favorite” your messages, mailbox providers like Gmail or Outlook are much more likely to ensure that your messages are delivered to a recipient’s inbox.

Clean Out Poison Addresses

Most of the email addresses in your list will be acquired through an online form. And with most online forms there is inevitable bot traffic or “form spammers,” where the email addresses entered are not associated with a person who is interested in your content or products. The reasons behind these illicit form completions are varied, from email relay hack attempts to security breaches to link spam and more, but the savvy email marketer will ensure these are removed from all lists.

Why? The primary guideline is that every email you send should be a wanted email. Addresses used by bots do not correlate to a “real” email or to a recipient who wants your content. Beyond this, there are security and email reputation issues with sending messages to unverified addresses.

But there is more. Did you inherit a list, rent one, or add someone else’s list into your own? A responsible marketer would never buy a list to target via email. But in case you know someone who is tempted, it’s important to understand some history.

In ancient times, some marketers engaged in the questionable activity of email harvesting. Email harvesting was a method of building email lists by deploying crawlers or bots that scan public or private content to extract email addresses. To combat this, some mailbox providers or filtering service providers placed “honeypot” addresses as traps, and blacklisted servers/domains that sent to those addresses. An email blacklist is a list of IP addresses or domains that are suspected of sending spam or sending to harvested (or poisoned) lists. Some blacklists are publicly searchable, and some are kept private by mail service providers. You now know the danger in buying and using a list that might include these email addresses.

An attendee of one of my sessions stood up and challenged me to come up with any scenario where procuring an email address list could be of some advantage. I could think of only one use, and that would be specific to digital advertising—to upload a high‐reputation email address list to test custom audiences on platforms that support it (many do). But adding any of those addresses to your own subscriber list directly would be like adding poison to your company’s marketing mix. Earn each subscriber address and confirm it is from a person who genuinely wants your email messages and campaigns.

Deliverability

One important principle to remember is that wanted emails get opened and delightful emails earn interaction. Interactions (opened, clicked, forwarded, or “favorited”) improve your deliverability. Email deliverability measures how many of your sent emails are delivered to recipients’ inboxes. As our incoming mail load increases, mailbox providers continue to develop ways to detect unwanted messages, and they categorize mail in a way that helps the recipient focus on what’s important or urgent as needed.

Filtering Spam  You might wonder how filters attempt to block messag‐es that look like spam and how this affects your deliverability to the inbox.

Imagine that you run the Gmail team at Google or the Outlook team at Microsoft or an ISP who provides email mailbox services. One of your primary objectives is to ensure your users only see legitimate, wanted emails in the inbox, to route promotional emails accordingly, and block unwanted and dangerous emails.

How do you do it? You might try the following:

1. Filter emails that have spammy words, phrases, or punctuation, like FREE!!!! Or the latest scam phrases, like “Passive Income.”
2. Detect messages from sending servers or domains that have sent a high volume of messages with largely the same content in a short period of time and block them or categorize them as “promotional.”
3. Block sending servers or domains that have a high rate of unsubscribes or deletion.
4. Block sending servers or domains that have a bad reputation already, such as those that are blacklisted or are associated with open relays.
5. Block sending servers or domains that have a no established reputation and are also triggering numbers 2, 3, or 4.
6. Block messages that contain only a single image.
7. Detect messages that have excessive CSS or HTML, tables, or indicators common to newsletters and categorize them as “newsletters” or “updates” instead of inbox.
8. Categorize messages with the word “unsubscribe” as mass emails.
9. Block messages that contain attachments that could be dangerous or offensive.
10. Detect messages with complex tags on links or tracking pixels and categorize them as “promotions.”

Now let’s look at the positive side. What signals would you look for to indicate a “wanted” email?

• A “starred,” favorited, or whitelisted email domain
• Emails with a high “read” or interactivity rate, e.g., replied to, forwarded, favorited, or images loaded
• Emails from a domain to which the recipient has already sent an email
• Emails with words or phrases that are used in conversational or transactional interchanges, e.g., “from your report” or “sales order receipt”
• Emails that differ significantly from others sent from the same domain in a short period of time
• Emails from sending servers or domains with established reputations and accountability systems

There are plenty of arguments about whether all of these checkpoints are in place, but most agree that they do reflect reasonable measures that could be used by mailbox providers. Here’s the key: when we craft our email campaigns and methods to avoid triggering these possible filters, we increase the chances that our emails will make it to the inbox. Now this isn’t about fooling the filters. Schemes like avoiding the word “unsubscribe” or trying to make a newsletter seem like a sales receipt will be a losing battle over time. Instead, the following sections discuss some methods that attempt to address these possible filters and may delight the recipient as well.

Email Frequency, Timing, and Limits  One technique that can increase open rates is to set email message timing to correlate with the times of day that a recipient has most often interacted with your business. Bulk sends can be batched by these time blocks over a day or even a week. So if Raul subscribed at midnight in his time zone, messages from my servers will be sent to him within two hours on either side of midnight. If Ayat clicked at 2 p.m. in her time zone, then you could update her sending time to be a few hours on either side of 2 p.m. in her time zone.

It is a common practice for email marketers to put limits on total outbound emails per minute, per hour, and per day. This is called “throttling.” Email throttling is the process of limiting how many emails are sent from your servers in a given time frame. For example, we might limit our sending server to 1,000 emails per hour. Controlling the volume can help reduce the indicators that suggest your messages are spam. Remember, if you ran an email service and detected, say, 900 emails per second from the same sender to your clients, it would be pretty easy to label that as a bulk or promotional email.

For larger entities, it is a healthy practice to put limits on total number of emails sent to any one recipient in a set period, excepting transactional or customer support emails. A sudden high volume of emails to one recipient increases the chances of earning a spam label or an unsubscribe from the recipient.

Other Techniques to Increase Deliverability  Besides the preceding practices, email marketers should be aware of a few vestigial indicators.

• Spammy words: In the early 2000s, Microsoft Outlook was prone to mark a message as spam if it included specific words—even certain names generated a spam score. While mailbox providers are using more advanced methods now, it still helps to avoid using words and punctuation that correlate with spam emails. Words like “FREE!” in the subject line or “make more money” in the body are obvious examples. You can browse the content in your spam folder to get ideas for the most recent phrases to avoid.
• Complex code: Emails with complex CSS or extraneous HTML are reported to trigger spam filters. It’s unlikely that a person‐to‐person email has 200 lines of HTML for each paragraph. So here again, it can help to simplify. Favor technology that keeps HTML, CSS, and formatting directives simple.
• One last practice that could seem counterintuitive to sum up the deliverability section: Be genuine. If your email is a newsletter, then don’t attempt to portray it as something else. I often call out [Newsletter] in the subject text so subscribers know exactly what is being sent. Wanted emails are opened and read, and opened emails help your reputation directly or indirectly. Yes, your newsletter may be categorized as a “Promotion” or “Update” but this is better than eroding trust or earning an unsubscribe.

The overall rule for deliverability, aside from some vestigial technical faux pas to avoid, is to generate content that is wanted and eagerly anticipated.