Dear reader: This blog post is vintage Appboy. We invite you to enjoy the wisdom of our former selves—and then for more information, check out our new Cross-Channel Engagement Difference Report.

Okay. So you’ve finished the technical steps to get your email program configured correctly. You’ve gone through the IP warming process. You and your team have come up with the most engaging and killer content that you know is going to resonate with your audience. You start sending live campaigns. Now what?

Whether you’ve been sending email for years or you’re just starting out, knowing what email metrics to pay attention to is crucial to ensuring the long-term success of your email program. Here are key metrics to watch:

1. Open Rate

Your email open rate is the total number of email opens your messages receive, divided by the number of emails delivered. The open rate should give you a good sense of your audience’s overall audience engagement, including repeat email openers and other outliers.

2. Click Rate

Your email click rate is the total number of clicks your emails receive, divided by the total number of emails delivered. Like your open rate, your click rate gives high-level insights into your customers’ engagement with your email program, including customers who come back to an email to re-engage.

3. Unique Open Rate

Your unique open rate in a given email campaign is the total number of unique recipient email opens divided by the number of emails delivered in the campaign. That means that if one of your customers opens a given campaign five times, it only counts as one unique open, but five total opens. This metric can help make it clearer how your subject line is performing, since it’s the first piece of content that users see and is instrumental in nudging them to open the email in the first place.

4. Unique Click Rate

Your unique click rate in a given email campaign is the total number of unique recipient email clicks divided by the number of emails delivered in the campaign. That means that if one of your users clicked on all three links in an email you sent, they’d generate three clicks, but only one unique click. In general, a high unique click rate is a strong indicator of a clear, strong call-to-action (CTA), since that’s the primary driver of in-message clicks.

5. Click to Open Rate

Your click to open rate is calculated by dividing the number of unique clicks that your emails received with the number of unique opens. In other words, out of everyone that opened, how many clicked? In general, if the subject line of the email does a good job matching the message’s body and main CTA, you’ll see a stronger click to open rate for that campaign.

6. Open Rate by Domain

Your open rate by domain is the number of email opens for users on a given domain—think Gmail, Hotmail, etc.—divided by the number of emails delivered to that domain. This metric can be useful if you’re looking to understand how your email campaigns are performing at different ISPs/mailbox providers, and whether you have deliverability issues at a particular domain (Gmail, for instance).

7. Click Rate by Domain

Your click rate by domain is the number of email clicks for users on a given domain—think Gmail, Hotmail, etc.—divided by the number of emails delivered to that domain. This metric can provide clues when your email is being negatively impacted by domain differences in how messages are displayed in users’ inboxes, among other insights.

8. Hard Bounce Rate

Your hard bounce rate is the number emails that weren’t delivered due to invalid or nonexistent email addresses divided by the total number of emails sent. Keeping an eye on this metric can give brands insight into how much of their of the email list is inaccurate or out of date.

9. Spam Report Rate

Your spam report rate is the number of email recipients who report your emails as spam divided by the number of emails you delivered. This metric can do a lot to highlight potential issues with your email, and to identify campaigns that may be driving up spam reports.

10. Unsubscribe Rate

Your unsubscribe rate is the number of people who unsubscribed from your email list divided by the number of emails delivered. As with your spam report rate, this metric can help brands better understand what campaigns are negatively impacting your email list size, making it easier to optimize future outreach.

When it comes to email metrics, where do you start?

There are metrics and benchmarks for every industry and every campaign type. That’s great, but it can make it hard to know where to start when you begin sending email campaigns to your customers. Complicating things further, every company has its own unique audience with their own unique preferences and engagement patterns. You may have a highly engaged young audience using your app, for example, but that doesn’t mean that that high engagement will directly translate into email. But if you just need somewhere to begin, there are general benchmarks that can be a useful starting point: average unique open rates in the 10-20% range and unique click rates in the 5-10% range are normal for traditional marketing messages.

However, it is not uncommon to see wide variance in the numbers for different campaign types. A real-time welcome email sent to confirmed email addresses might see unique opens in the 40-60+% range, while a re-engagement campaign to lapsing users might only see unique opens in the 3-5% range. It’s important to make sure that you track and report on these campaign types separately, in order to fully understand how your audience is engaging with the emails you send.

Building a culture of testing

Instead of fixating on what others in your industry are doing, consider building an internal culture of testing and iteration where you’re always striving to best the results you’re seeing today. The best marketers develop this ethos early on, and never settle for what works now—because your customers’ preferences will change over time. If you want to stay competitive, it pays to treat today’s winner as tomorrow’s control group.

Want to make that happen? Most marketing platforms make message testing easy enough that it’s possible to include some sort of test in every campaign you send. That test could compare subject lines (for instance, long subject lines versus short ones, or one that includes emojis versus one that doesn’t), examine the impact of different CTA sizes and colors, or whether messages perform better if they include personalization.

If you have a small team, or just need a simple test to get you started, consider beginning with a subject line test. You can even try to grab 20 seconds of your CEO’s time and have her choose which subject line she predicts will win. While it may seem small, watching that 15% unique open rate move up to 16 or 17% can start opening up that conversation on a broader company level. Keep the needle moving!

As you start developing a sense for how your users respond to different testing variables, you may find that you want to start incorporating conversion-focused metrics into the email metrics you’re tracking. That could be app installs, email sign-ups or registrations, or whether a given email campaign is driving app opens or online purchases. Which ones matter for you will depend on your specific brand and industry, as well as the goals of your customer messaging efforts.

Email metrics: What to watch out for

Okay, so you’re tracking these metrics—now, what can you do with them, and what can they tell you about the health of your email program?

We know that if there’s a sudden or unexpected drop in open rates at particular domain, this might be an indication of a deliverability problem to look into. If hard bounce rates are trending at a normal average of 3%, then suddenly spike to 10%, it might be an indicator of an email capture problem at sign-up or a new influx of users from a different registration source. If you properly set expectations at the time of sign-up, spam reports should be low or less than 0.08%. Anything higher and this should be a call to action to review the entire user journey from email capture to initial email engagements in the channel. If the content is relevant and engaging, and your audience knows to expect it, unsubscribe rates should generally be less than 0.3%, depending on vertical.

Any step change increase in unsubscribe rates is a warning sign that your content is not relevant, or perhaps frequency is too high. In that case, consider implementing a preference center with opt-down options, so that customers have choices other than just unsubscribing.

Beyond core email metrics, you will want to ensure you are tracking your primary conversion metrics that are important to your business. Is that pushing for app installs? Driving users to sign up to a premium service tier? Tracking these closely can inform your overall content and testing strategy to ensure your cross-channel engagement efforts are working for you and your users are finding value from the emails and other messages you send.

Having a strong understanding of what each and every metric means can help inform the way you analyze and track the effectiveness of your customer engagement campaigns. In addition, knowing what to watch out for can be just as important to ensure you promptly address any dips in performance that might be signs of more systemic problems to look into. The data is all there—let it work for you!