While math is universal, interpreting email statistics is more difficult. Here is a quick rundown of important email delivery metrics and what changes in those metrics might mean for your email program.

1. Change in count of attempted messages

If you send a large amount of email on a regular basis, your ESP will recognize that as normal sending. However, if your sending volume suddenly spikes to previous sends–and it’s quite a bit more–consider the reasoning behind the mass send.

If your email blast was an attempt to reach deeper into your full list of recipients to “win back” those that haven’t opened or clicked in a while, that difference in volume could harm your deliverability. Sometimes a wider reach (larger send) can actually reduce your delivery rates because inbox filters suspect this large send to be overly aggressive (aka “spammy”) marketing.

2. Count of attempted vs. delivered messages

This metric represents emails the mailbox filters did or did not deem worthy of the inbox. If you have a large number of emails not getting delivered at all, this can usually be attributed to blocks and bounces (see below for more of an explanation on the difference between blocks and bounces). And while some ESPs/UIs may use different terms for these two categories of undelivered messages, you can think of a “block” as a message that failed, but the address is most likely still valid. And a “bounce” can be thought of as failing because the destination (email) was invalid.

There are some gray areas in between, but ask your ESP how they define these undelivered messages and that will help you to know what went wrong and what to adjust for next time. Here are two example scenarios and responses for spikes in these metrics:

Large Increase in Bounces

Review your list signup/acquisition practices. If you have users sign up without knowing the address you gathered–such as during an auto-Facebook signup–provide them a chance to confirm that this is the right email to send to. Also, make sure you aren’t requiring an address just to access your site. This can lead to people providing fake addresses just to view the goods.

Large Increase in Blocks

Review the exact SMTP codes (aka block reasons) as they can range from “mailbox currently full” to “spammy content detected.” Obviously, the former warrants another message later on (unless you consistently get that block for that user, then it may be time to cut them loose from the list) and the latter warrants a content audit to ensure you’re sending valuable and useful content.

3. Percentage of opens compared to delivered messages

These metrics represent total recipients divided by the number of ones who decided to open the email. It shows who did or did view your email in the inbox, were enticed by your subject line, and then engaged.

There is no “good” universal open % that all marketers should strive for. Granted, there is the universal truth that lower is bad and higher is better. But, success can look different for different senders. Just know whether you are reviewing aggregate open rates (counting all open events and not just the first one that occurs per message) or unique open rates (counting only the first open event that happens per message).

Some businesses require a much higher rate to have a positive ROI and some businesses with larger ticket items may only require a small % of opens to realize a positive ROI. It is also best to review open % relevant to previous days for similar campaigns. Pay attention to how much your open rate went up or down compared to the expected open %. To achieve this, make sure you have open tracking enabled with your ESP.

5. Percentage of clicks compared to opened or delivered messages

These are recipients who recognized your brand, found you in the inbox, were intrigued to open your message, but didn’t click on any link. Similar to the “open %” there is no universally accepted click % : open % rate that all marketers should strive for.

When reviewing all business verticals and mail program statistics, a solid average for aggregate open rates (counting all open events and not just the first one that occurs per message) is 20%. And, for unique open rates (counting only the first open event that happens per message) we have seen 10% be a solid average.

Again, this is an average as some businesses will need a much higher rate to have a good ROI and some businesses with larger ticket items may only require a small % of opens to realize a successful ROI. Enabling “click tracking” with the ESP you are using helps you monitor and measure open rate success.

6. Large % of spam complaints or large increase in spam complaints

Ultimately, a spam complaint means your recipient doesn’t want your email. As inbox providers work to make sure that only wanted email reaches the inbox, this piece of feedback is invaluable to you as a sender.

Know when a user is marking you as “spam,” by activating all necessary “feedback loops” for the mailbox providers you would like to track. SendGrid turns on all IP and domain based feedback loops for all known mailbox providers that provide them. You can also access and digest the data on your own through our Forward Spam setting.

Stop sending email to a user who has marked your message(s) as spam.

A high spam complaint % that is related to any of the sending elements (i.e. IPs, domains, links, templates, images, etc) included in your mail can cause you to be delivered directly to the spam folder or blocked completely by certain mailbox provider filters.

Always remember to compare this very closely to your open rate which reveals if you are sending valuable and wanted content by showing who wants your mail (opens) compared to those that don’t (spam).

7. High % of unsubscribe requests

These are recipients who were interested in your mail at one point (if you have a proper opt-in process), but who no longer wish to receive mail from you.

In order to be CAN-SPAM compliant, make sure you have a working unsubscribe function in all marketing messages. SendGrid has a “subscription tracking” tool that automatically adds an unsubscribe link to each message and also adds the recommended “List-Unsubscribe” header to your message headers.

Stop sending email that receives high unsubscribes and never send marketing email to a user that has unsubscribed from your marketing emails.

Remember that it is great to be aware of which mail or segment a user unsubscribed from. But, if you are ever unsure, it is best to err on the side of caution and remove them from all marketing mail. A user is much more likely to mark future messages as spam if they thought they unsubscribed from that brand and continue to get mail.

For more information on how to optimize your email program, check out our Email Marketing Survival Kit. 

Jacob comes from a background in technical account management and delivery analysis for the last six years, and has been with SendGrid's Deliverability Consultant team for the last two years. He enjoys spreading knowledge to help the email community send more "wanted email" and to help senders realize their full potential. Originally from Nebraska, but living in Colorado long enough for it to feel like home, Jacob enjoys a lot of what the Denver restaurant, bar, brewery and music scenes have to offer.