Improving Your Email Deliverability

Spam – it’s everywhere.

Spammers (don’t get me started) are cramming our inboxes with an endless stream of junk mail, and have been since the Internet was in digital diapers. To combat this, safeguards have been put in place to screen out these unsolicited emails from non-existent Nigerian princes and fly-by-night pharmaceutical companies.

And that’s a good thing. Unfortunately, spammers don’t give up so easily and these spam filters – try as they might - can’t always discern between junk mail and our own legitimate emails we’re trying to disseminate to a list of recipients. Which is why a certain percentage of our emailed messages get tagged as spam and are undelivered or relegated to a junk/spam folder.

But don’t despair, mon frere. There are tips you can learn and techniques you can master that will help shepherd your emails to their ultimate destination. But to grasp them will mean taking a deep dive into the world of email deliverability.

Maintaining Your Rep

What exactly is email deliverability? Basically, it’s the measured likelihood of your emails being successfully delivered to your recipients’ inboxes. Seems straightforward enough. So what’s the problem?

The first thing to understand is, your email deliverability is profoundly affected by the IP reputation of your sending email server (which, I hope, is an ESP or CRM – more on them below). That IP reputation is based on your email sending habits (i.e., the volume of emails you send at one time, the frequency you send out emails, how many of the addresses you’re sending to are active vs inactive, complaints from recipients, etc.).

All that information is collected by your recipients’ server, usually a mailbox provider like Outlook, Yahoo and Gmail, to determine whether or not you’re a spammer. (I checked – you’re not.)


Oh, goody – abbreviations. Interesting how simplifying things (i.e. acronyms) can sometimes make them more difficult (having to learn a new language—acronyms).

Worry not. I’ll keep it as simple and relevant to this discussion as possible.

First, what’s an ESP? An ESP stands for Email Service Provider. It’s a digital platform whose services you purchase from a company to send out a large volume of emails to a list of recipients. It’s somewhat similar to a standard mailbox provider (like Google or Outlook), but in addition to sending out all those emails, an ESP can also tell you how your campaign performed by allowing you to view how many and which of your recipients actually opened your emails along with any messages that bounced. Sweet.

A CRM stands for Customer Relationship Management. It, too, can usually send out a large volume of emails to a list of recipients, monitor which emails were opened, and which bounced. But in addition, a CRM is a vastly more powerful tool for performing multiple other tasks completely unrelated to emails. However, for the purposes of this discussion, we’ll just focus on the email delivery side of it.

So basically, ESPs and CRMs are two good options if you need to send out a lot of emails at one time.

You Can Call Me Al-(gorithm)

Now here’s where things get tricky. When you (through your CRM or ESP) send out a large volume of emails, chances are your recipients don’t all use the same mailbox provider, so you’re actually sending emails to as many as a dozen different mailbox providers, such as gmail, hotmail, aol, etc.

To complicate matters further, each of those unique mailbox providers have their own proprietary algorithm designed to analyze the IP reputation of incoming emails. Their only job is to detect and filter out spam. And because spammers are constantly detecting loopholes and slipping through those spam filters, each of these algorithms are constantly being updated in response.

Unfortunately, this means that while your server’s IP reputation might pass the smell test of one particular mail provider, if their algorithm changes (and it will, sometimes on a daily basis), your email - which was perfectly acceptable just days or even hours before - may suddenly be flagged as spam after those latest tweaks to their algorithm have been implemented.

Now multiply this scenario by up to a dozen different mailbox providers, each with their own constantly changing algorithms, and you begin to see the problem. Oy vey.

So instead of ALL of your emails being delivered to the inboxes of each and every recipient on your list, only a certain percentage of them get delivered. Quick example: Let’s say your email deliverability rate was 80% (some of which could have ended up in their junk/spam folder). That means 20% of your emails were not delivered to your intended recipients at all. Apply that percentage over the course of an entire email campaign, and we’re talking a lot of missed messages and lost opportunities.

But don’t throw in the towel just yet.


Here a few simple steps to improve your email deliverability

(that apply to most, if not all, email providers.)

1. Mind Your Language

Remember those spam filters the mail providers use to determine whether your email is legit or not? Well, one of the things they look for are “spam triggers.” These are words and/or phrases that appear either in your subject line or the body of your email that are often used by spammers. Examples include “free cash,” “extra income,” or “save $.” Avoid these as much as possible. Also, try to tone down the use of certain punctuation like “!!!” and writing in all caps. They have higher spam ratings too.

2. Cleaning Your List Should Be Top of Your List

It’s counter-intuitive, I know, but you don’t want to send out emails to just everyone. Instead, you should regularly review and reduce your mailing lists down to those contacts who are most likely to interact with your emails (i.e., click, reply, and forward your emails). Why? Because their mailbox servers will factor this activity (or lack thereof) into your server’s IP reputation. The more active your recipients are, the higher your IP reputation will be (but also, vice versa).

So, unsubscribe and/or remove any inactive contacts whose emails keep bouncing. Again, your recipients’ mailbox providers are on the lookout for bounced emails, and will ding your IP reputation if they start mounting up.

To determine activity, you might consider a double opt-in, where a recipient is asked to verify that they actually want to receive emails from you by responding “yes” to a second confirmation email. Anyone who does reply positively to such a request is a pretty sure bet for future activity.

Also, never ever continue to send to an email address who has opted out. Not only is it against federal regulation to do so, it’s a sure way to have those recipients report you as actual spam, which will definitely hurt your sender reputation.

The key is to keep your mail lists as clean and streamlined as possible, which means you need to periodically review and edit them down wherever and whenever necessary. This is probably the single most critical piece of advice you should take to heart. It may not be the most glamorous of tasks, but it will have the single biggest impact on your email deliverability.

3. Predictability is a Plus

Scheduling your emails through your EPS or CRM to be delivered on a consistent and predictable timetable can also protect your email deliverability/IP reputation. Why? First, because it helps reduce email spikes, which are another red flag to the mailbox providers that you might be a spammer. But it also encourages activity on the part of your recipients.

How does that work? Well, if you establish a schedule of sending out an email with a special weekend offer every Friday at noon, recipients will be more likely to look for, open, and respond to that email. That activity on their end is noted by the mailbox providers, and your IP reputation benefits accordingly.

4. Be the Master of Your Domain

Earlier, we established that your IP reputation is based on your email sending habits, which includes the volume of emails you send at one time, the frequency you send out emails, how many of the addresses you’re sending to are active vs inactive, etc.

But that’s not the only thing your recipient’s mailbox receiver is factoring into its calculations when deciding if you’re a spammer or not. It’s also looking at the site that the email is being sent from. This is called the sending domain and sending IP address.

I mentioned earlier the advantages of using either ESPs or CRMS when sending large volumes of email. Here’s another reason you should consider doing so.

You could send mail from a server at an ISP (like Verizon, Comcast, Cox, etc.) or from a virtual machine in the public cloud (like Amazon or Rackspace.) But doing so could lower your IP reputation because that IP can be used by many different people and can often change hands without notice. So, if someone uses it to send spam, your own IP reputation can take the hit.

Note: Some ESPs do use shared domains and shared IPS, but a good company will ensure that they use only reputable ones.

All Things Considered

As mentioned before, each mailbox provider’s algorithm is different. Once an email is received by a particular recipient’s mailbox provider, it’s difficult to know exactly which criteria are factored into their calculus of whether or not to accept your email or file it in the junk/spam folder. But it’s a fair guess to say at least some of the following factors are considered when making their final decision:

  • The ratio of images versus text (try to follow the 80/20 rule: 80% text to 20% images).
  • Previous engagement between the sender (you) and a specific recipient.
  • Overall engagement from all recipients on your mailing list.
  • The “reply to” address and how it relates to the source domain.
  • Historical sending patterns.
  • IP/domain reputation.
  • Errors in the email’s code

(Credit: Kajabi)

There are a number of things you can do to improve your email deliverability, but at the risk of sounding like your mother – clean up your lists! I know you have other stuff to do, but you simply have to prioritize this. Otherwise, at least some of the money and time you invest in an email campaign is going to be wasted.

With that said, I hope this foray into the world of email deliverability is of some value. There’s a lot of terminology and abbreviations that can make the subject seem more than a little daunting. But once you sort through all the technobabble, the concepts themselves are not so hard to grasp. 

Unlike spammers, who are impossible to grasp, those slippery, little slime-balls. Don’t get me started on them.

Written by Kinn Melby – Vast Action, Inc.
Image by Vast Action, Inc.

Know someone who’d benefit from this article? Please share it with them!

Have anything to add that would be useful for others to read? Let us know. We love sharing knowledge and having knowledge shared with us.



50% Complete

Two Step

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.