There are many important metrics to monitor when it comes to identifying the quality of an ESP or your own email marketing system.

Two of these are very important when it comes to having your subscribers actually receiving your messages.

The one is easy to measure and report on, while the other is much more fluid and extremely hard to accurately track and report on.

Let’s dive into those two metrics now …

Delivery Rate

It is not uncommon to see something like “99.97%” delivery rate quoted.

What exactly is the delivery rate?

It is basically just the number of messages that were accepted by the receiving mailbox provider, but, it does not in any way show how many messages are actually making it to the inbox of the subscribers.

So, if an ESP is sending 10,000 messages, and 9,987 of those messages are accepted for delivery by the inbox providers, this means that the ESP can then claim 99.87% delivery rate.

This is calculated by: 9,987 divided by 10,000 = 0.9987 times 100 = 99.87.

To be clear here, the ESP is not lying nor deceiving anyone. They are just not stating that the metric being given is nothing more than the number of messages that were accepted by the mailbox provider, and is no indication whatsoever as to where these messages are landing.

Obviously it is important to get the messages accepted by the mailbox provider, but, what is more important is how many are actually making it to the inboxes of their customers.

If the delivery rate is low though, anything below 98%, that in itself is indicative of a much bigger and deeper problem at said ESP, or your own email marketing system if you are mailing from your own system.

The low number is a sign of:

  • High bounces
  • Low list quality
  • Low customer quality

A high delivery rate in no way guarantees high inbox rates, BUT, a low deliverability rate almost certainly guarantees that a high % of messages are going to the spam folder at inbox providers due to bad ESP reputation with them.

Deliverability Rate

The much more important metric to track here is the Deliverability rate.

This is much more difficult to track though, and no ESP actually quotes a Deliverability rate purely because it is such a difficult metric to track.

Let’s dig into how exactly the deliverability rate can be measured:

  1. Seed listsA Seed list is a list of email addresses added to the main outgoing email and are monitored automatically for where they land at the mailbox provider.In theory this is a great idea and works well for the smaller mailbox providers which has simple spam algorithms, but, for the bigger, more complex mailbox providers like Gmail, these are all but useless.
    • Gmail will for instance put the same message from the same sender in the inbox of 1 subscriber, while putting it in the spam folder of another subscriber. This is not conjecture, this has been tested and proven many times over.
    • The reason for this is all about their algorithms measuring things like engagement, sending IP reputation, sending domain reputation, links in the email reputation, engagement from the subscribers, past interaction with senders by the receiver, and a whole horde of things they don’t ever make public.
    • In a future post I will dive deep into individual-level filtering.
  2. Tools that have access to your inbox provider through an API
    • eDataSource owns Boxbe and uses it to accurately monitor the actual placement of messages sent by ESP’s and other bulk mailers. The problem with this approach is that the end-users have to actually grant permission to Boxbe to read all their email all the time. They need enough users using the system to make the statistics viable, and also of course to make sure that most of the email being sent are actually seen to be able to report on it.Boxbe is a very useful service on it’s own, but, in today’s day and age where there is a very strong focus on personal privacy, I have to wonder how long a service like this will last.
    • Boxbe is not the only service like this owned by a company that provides data on email placement at inbox providers. There are a few others.Please note that I do not condemn these services in any way. They serve a purpose, and like in the case of Boxbe, they are actually very useful to the end user.

Inbox Placement Factors

There are several factors that contribute to inbox placement, many of them outside the control of the ESP, making it even harder to give a true inbox rate metric.

All the factors are outside the scope of this article, but, let’s have a quick look at some of the major ones …

  • From name

    This is the first thing any subscriber to your list looks at. They need to immediately recognize it to ensure they open it, to begin with.

    The more subscribers open and interact with your messages, the better your reputation with said inbox provider, and the higher the probability of your message being placed in the inbox of the subscribers.

    Consistency is key here and it is highly suggested that once you start using a specific from name, you rarely, if ever, change it.

  • From address

    Very much the same as the From Name, although many subscribers won’t look too closely at the from email address, the mailbox providers DO look at this, and the from email address does build a reputation with the mailbox provider, so, again, be consistent with your from email address, and rarely, if ever, change it.

    It still AMAZES me that some companies and email marketers use a no-reply@ address as their from email address! You WANT the subscriber to actually reply to your email! It is not JUST about getting a better inbox rate, but, it is ALSO about the fact that email is really a one-to-one medium!

    More on no-reply@ in our next post! ;-)

  • Subject Line

    This is the second thing that a subscriber looks at.

    The subject line “sells” the open. As mentioned in the from name part above, the more subscribers open your email and interact with your email, the better your engagement reputation becomes with the mailbox provider, and the more likely it is that the mailbox provider will place your email in the inbox of the subscriber.

    BUT … Do NOT, under ANY circumstances use deceptive subject lines!

    Not only is it illegal, but, it will alienate your subscribers and greatly increase the likelihood of the subscriber marking your message as spam!

  • Content

    Whereas the subject line “sells” the open, the content “sells” the action.

    The action of an email is not always to have the subscriber click a link. It could be to get them to respond to your message, or, get them to make a phone call, or, get them to go to a physical location.

    The better and more engaging your content, the higher the chances of the subscriber to take the action that you are intending for them to take.

  • Engagement

    Engagement is critical for your continued success with your email marketing program and is one of the highest value metrics that Mailbox Providers look at.

    Engagement is things like:

    • Opening the email
    • Replying to the email
    • Clicking a link in the email
    • Moving the email into a folder