There are several key metrics that should be used to measure the success of an email marketing strategy effectively. Tracking the right metrics is important to determine how well the emails are performing and if the strategy needs any adjustments over time. Some of the most important metrics to track include:

Open Rates – One of the most basic but important metrics is the open rate which measures how many recipients actually opened each email. Open rates help determine if the subject lines are enticing enough for people to take a look at the content. It’s a good idea to track open rates over time and benchmark them against industry averages for the sector. Open rates of 20% or higher are generally considered good but the goal should be continuous improvement over time.

Click-Through Rates – After measuring opens, tracking click-through rates from email content to the desired destination URLs is crucial. CTRs help determine which content and call-to-action buttons are most effective at driving people to the website. clicks within the body of emails and footers should be tracked separately. CTRs of 2-3% from content links or 5-10% from CTAs are generally seen as good performance.

Unsubscribe Rates – Also important to measure is the unsubscribe rate which shows the percentage of people who choose to unsubscribe from a particular mailing list. Higher unsubscribe rates could indicate people are receiving emails they don’t find relevant. Unsubscribe rates below 1% are ideal.

Engagement/Interaction Rates – Beyond just open and click metrics, it’s valuable to measure engagement rates that track actions like social sharing, form submissions, content downloads, etc. This helps determine if emails are effective at driving real interactions and conversions beyond just initial clicks.

Conversion/Revenue Metrics – The most important metrics focus on conversions and revenue. These include metrics like e-newsletter signups, webinar/event registrations, website registrations, lead submissions, e-commerce purchases and sales revenue that can be directly attributed to email interactions. Goals and return on investment should connect email metrics back to conversion and revenue results.

Subscriber/List Growth – Over time, the email list size and growth rates are also important to track. Steady growth of the list size shows improved acquisition strategies while flat or declining numbers may indicate issues. Growth of targeted lists is better than overall general growth.

Delivery and Spam Rates – Ensuring high email deliverability is critical to the strategy’s success as well. Tracking metrics around successful email deliveries, spam complaint rates and bounce rates help spot any red flags impacting overall performance.

Benchmarking – Along with benchmarking key metrics against past performance, it’s good practice to benchmark email marketing KPIs against relevant industry averages provided in reports from experts like Litmus, Mailchimp, etc. This helps assess if results are above or below expected norms.

Segment-level Analytics – Drilling down metrics to see performance of different email list segments, content categories and device types (mobile vs desktop) provides actionable insights. For example, transactional emails may have different benchmarks than marketing emails.

Attribution Modeling – Advanced attribution techniques can begin linking final conversions back to specific emails, campaigns, links, or media that contributed to a sale or lead. This improves ROI justification and optimization of attributing budget/efforts.

Qualitative Feedback – In addition to quantitative metrics, occasional qualitative surveys can gather customer feedback on email preferences, content relevancy, and improvement ideas. This user sentiment helps supplement the quantitative metrics.

Testing and Optimization – Consistent a/b split testing of subject lines, send times, call to action buttons, and design/formatting helps optimize different email elements. Winners of each test round can be implemented to continuously enhance email performance.

It’s important to track a balanced set of relevant metrics at different stages of the customer journey that measures email strategy success based on multiple dimensions – from initial engagement and interaction levels to conversions and renewals further down the line. Combining quantitative metrics with occasional qualitative surveys provides invaluable insights to evaluate progress, refine approaches, and improve ROI from the email marketing strategy over the long-term. Continuous testing helps make ongoing enhancements to keep email performance improving over time.