Key Metrics & Terms

Understand essential email marketing metrics to measure success and improve your campaigns with Brew

Email Marketing Metrics Overview

This page explains what each email metric means and defines essential terms, so you can better analyze your performance and ask smarter questions.

The basics—sends, opens, and clicks—are right there in your email dashboards. But when you’re ready to dig deeper into things like bounce rates or spam complaints, that’s where Brew’s Ask AI feature comes in handy.

What’s on This Page

Navigate to the section that interests you most:

Core Engagement Metrics

• Open Rate - How compelling are your subject lines?
• Click-Through Rate (CTR) - How engaging is your content?
• Conversion Rate - Are you driving business results?

Deliverability Metrics

• Bounce Rate - Are your emails reaching recipients?
• Spam Complaint Rate - Is your content relevant?
• Unsubscribe Rate - Are you respecting preferences?

Strategic Insights

• Open Tracking & Deliverability - Understanding tracking limitations
• Focus on Business Impact - Moving beyond vanity metrics
• Advanced Metrics Analysis - Using Brew’s AI features

Reference

• Email Marketing Terms - Complete glossary with 25+ essential terms

Core Engagement Metrics

Open Rate

Open rate shows the percentage of delivered emails that were opened by recipients.

$Open\ Rate = \frac{Number\ of\ unique\ opens}{Number\ of\ emails\ delivered} \times 100$

This metric reflects how compelling your subject line and sender name are. It’s your first indicator of audience engagement.

How Open Rates Are Tracked

When you send an email through Brew, here’s exactly how opens are measured:

1. Tracking Pixel Insertion: A 1×1 pixel transparent GIF image is automatically embedded in each email you send. This invisible pixel contains a unique identifier linked to both the specific email and the recipient.
2. Email Delivery: Your email is delivered to the recipient’s inbox with this tracking pixel included.
3. Image Loading: When a recipient opens your email and their email client loads images, it requests this pixel from Brew’s servers.
4. Open Registration: This server request registers as an “open” in Brew’s analytics system, recording who opened the email and when it happened.
5. Data Processing: Brew consolidates this data to calculate your open rate, filtering out duplicate opens from the same user to provide unique open metrics.

Why open rate matters

A higher open rate means more people are seeing your message. It’s the gateway to all other engagement.

Generally, an open rate in the range of 17–28% is considered average to good, with recent industry benchmarks around 21% overall.

Limitations to consider

Open rates have become increasingly unreliable due to privacy protections and technical limitations. Here’s what affects accuracy:

Privacy Protection Impact:

• Apple Mail Privacy Protection (iOS 15+): Automatically pre-loads tracking pixels, causing emails to show as “opened” instantly whether actually read or not
• Corporate email security: Many companies use firewalls that cache or block tracking pixels, leading to false opens or no tracking at all
• Email client defaults: Some clients block image loading by default, preventing open detection entirely

Gmail-Specific Issues:

• Message clipping: Emails over 102KB get clipped by Gmail, preventing open tracking unless recipients view the full message
• Preview panes: May trigger tracking pixels even when emails aren’t fully read
• Promotional tab filtering: Can delay or prevent image loading

Why this matters for your strategy:

• Open rates can be artificially inflated by up to 30-40% due to privacy protections
• Focus more heavily on click-through rates and conversions as reliable engagement indicators
• Use open rates as directional guidance rather than precise measurements

Better alternatives:

• Track specific actions like downloads, sign-ups, or purchases
• Monitor website traffic from email campaigns using UTM parameters
• Analyze revenue attribution from email marketing efforts

Use Brew’s Ask AI feature to ask questions about your open rate performance, such as: “What subject line patterns have led to the highest open rates for my newsletter?”

Click-Through Rate (CTR)

Click-through rate (CTR) is the percentage of delivered emails that resulted in recipients clicking a link within the email.

$CTR = \frac{Number\ of\ unique\ clicks}{Number\ of\ emails\ delivered} \times 100$

CTR reflects how engaging and relevant your email content is, and how effective your calls-to-action are at driving action.

How Clicks Are Tracked

Brew tracks clicks through a process called link rewriting:

1. Link Modification: When you create an email, Brew automatically rewrites all links to route through our tracking servers before redirecting to the final destination.
2. Unique Identifiers: Each rewritten link contains parameters that identify both the email campaign and the specific recipient.
3. Click Registration: When a recipient clicks any link, they first connect to Brew’s tracking system, which records the click event along with relevant data (which link, which recipient, timestamp).
4. Instant Redirect: After registering the click, the recipient is immediately redirected to the intended destination URL. This happens so quickly that recipients don’t notice any delay.
5. Reporting: Brew aggregates this click data to calculate metrics like CTR and identifies which specific links received the most engagement.

Why CTR matters

Clicks represent the next level of engagement beyond opens. They indicate that your message was compelling enough for recipients to take action.

Across industries, a 2–5% CTR is common for email campaigns, with around 2.3% being the average.

Use Brew’s Ask AI feature to explore your click rate data with questions like: “Which types of links get the most clicks in my emails?” or “What content sections drive the most engagement?”

Open Tracking and Deliverability

Important consideration: While open tracking provides valuable insights, it can impact where your emails land in recipients’ inboxes.

How tracking affects deliverability:

• Promotional signals: Tracking pixels are commonly used by marketers and spammers, so inbox providers may flag emails with tracking as promotional content
• Spam detection: Some email providers use the presence of tracking pixels as one factor in spam filtering algorithms
• Transactional email impact: For transactional emails (receipts, confirmations, password resets), tracking pixels can reduce inbox placement since these should appear more “system-generated”

Brew’s approach:

• Smart tracking: Brew automatically optimizes tracking implementation to minimize deliverability impact
• Automatic optimization: Brew handles tracking decisions behind the scenes, balancing insights with inbox placement
• Focus on actionable metrics: Since tracking is automatic, focus your analysis on click tracking and business metrics that drive real outcomes

Pro tip: For critical transactional emails, prioritize inbox placement over open rate tracking. You can still measure success through completion of the intended action (password reset, account verification, etc.).

Conversion Rate

Conversion rate measures the percentage of recipients who completed your desired action after receiving your email.

$Conversion\ Rate = \frac{Number\ of\ people\ who\ completed\ the\ desired\ action}{Number\ of\ emails\ delivered} \times 100$

Why conversion rate matters

Conversion rate is crucial because it measures the business impact of your email campaigns. While opens and clicks are important engagement metrics, conversions represent actual business outcomes.

Tracking conversions

To track conversions, you’ll need to:

1. Define the specific action that constitutes a conversion for each campaign
2. Add UTM parameters to your email links
3. Connect your analytics platform to track these actions

Deliverability Metrics

Poor email performance metrics can impact your deliverability and account status. To protect your email reputation and comply with email regulations, Brew monitors your performance and may temporarily suspend your account if you exceed these thresholds:

• Spam complaint rate above 0.08% (less than 1 complaint per 1,000 emails sent)
• Bounce rate above 2% (20 bounces per 1,000 emails sent)

These safeguards ensure all Brew users maintain good sending practices and protect the deliverability of the entire platform.

Bounce Rate

Bounce rate measures the percentage of emails that could not be delivered.

$Bounce\ Rate = \frac{Number\ of\ bounced\ emails}{Number\ of\ emails\ sent} \times 100$

How Bounces Are Tracked

Brew tracks bounces through automated feedback from email servers:

1. Delivery Attempt: When your email is sent, it goes through multiple servers before reaching its destination.
2. Bounce Detection: If a receiving mail server cannot deliver the message, it sends back an automated response (an SMTP error) with a specific reason code.
3. Classification: Brew’s system automatically categorizes these bounce responses into hard bounces (permanent failures) or soft bounces (temporary issues) based on the error codes and message.
4. Recording: The bounce is logged in your campaign metrics along with the specific reason for the failure.
5. Automated Handling: For hard bounces, Brew automatically suppresses the email address to prevent future sending attempts, protecting your sender reputation.

There are two important types of bounces:

Hard Bounces

Permanent failures due to invalid addresses or blocked domains

Soft Bounces

Temporary issues like full mailboxes or server problems

Keep your bounce rate under 2%. This is the threshold at which Brew may temporarily suspend your account to protect your domain reputation and the deliverability of the platform.

Spam Complaint Rate

The spam complaint rate is the percentage of delivered emails that recipients marked as “Spam” or “Junk”.

$Spam\ Complaint\ Rate = \frac{Number\ of\ spam\ complaints}{Number\ of\ emails\ delivered} \times 100$

How Spam Complaints Are Tracked

Spam complaints are tracked through a standardized system called Feedback Loops (FBLs):

1. Recipient Action: A recipient clicks the “Mark as Spam” or “Report Spam” button in their email client.
2. ESP Notification: The receiving email service provider (like Gmail, Yahoo, or Outlook) captures this action and sends a standardized report through a Feedback Loop.
3. Complaint Processing: Brew receives these FBL reports and associates them with the specific email campaign and recipient.
4. Automatic Suppression: The complainant’s email address is automatically added to a suppression list to prevent any future emails from being sent to them.
5. Metric Calculation: Brew aggregates these complaints to calculate your spam complaint rate and provides alerts if rates approach concerning thresholds.

Aim to keep your spam complaint rate below 0.08%. This is the threshold at which Brew may temporarily suspend your account to protect your sender reputation and the deliverability of the platform.

Additional deliverability insights: Monitor your sender reputation regularly to ensure optimal deliverability. While Brew tracks essential metrics automatically, you can gain deeper insights into how different email providers view your sending reputation by using specialized reputation monitoring tools.

Boost your deliverability with self-engagement: Send a test email to yourself, open it, and reply to it. This simple action signals to email providers that your content is valuable and engaging, which can positively impact your sender reputation and improve inbox placement.

Unsubscribe Rate

Unsubscribe rate measures the percentage of recipients who opted out of future emails.

$Unsubscribe\ Rate = \frac{Number\ of\ unsubscribes}{Number\ of\ emails\ delivered} \times 100$

How Unsubscribes Are Tracked

Brew tracks unsubscribes through an intuitive preference management system:

1. Unsubscribe Link: Every email sent through Brew includes a legally-required unsubscribe link, typically in the footer. This link contains a unique identifier for the recipient.

2. Preference Center: When a recipient clicks this link, they’re taken to your branded Preference Center rather than being immediately unsubscribed. Here they can see all your subscription groups with descriptions.

3. Granular Control: Instead of a single “unsubscribe from everything” option, recipients can use toggle switches to choose which specific content types they want to continue receiving. This reduces total unsubscribes by letting contacts opt out of only the content they don’t want.

4. Immediate Processing: When a recipient updates their preferences, Brew instantly records these changes and updates their status in your audience.

5. List Suppression: The system automatically ensures this contact will no longer receive emails from the unsubscribed groups, while still allowing them to receive content from groups they remain subscribed to.

Most email experts consider an unsubscribe rate below 0.5% to be normal.

Brew automatically handles the entire unsubscribe process for you. Unsubscribed contacts are skipped when sending campaigns and automations, but they will still receive transactional emails (like password resets and order confirmations) since these contain essential information. This behavior ensures compliance with CAN-SPAM regulations, which distinguish between marketing and transactional communications.

Learn about the Preference Center

Customize how subscribers manage their email preferences with your branding

Learn about Subscription Groups

Create content categories that give subscribers more control over what they receive

Focus on Business Impact

While engagement metrics like opens and clicks provide valuable insights, the most important question is whether your emails drive meaningful business results.

Move beyond vanity metrics:

• Revenue attribution: Track how much revenue can be attributed to specific email campaigns
• Goal completion: Monitor actions that matter to your business (free trial signups, demo bookings, feature adoption)
• Customer lifecycle: Measure how email marketing influences customer retention, upgrades, or referrals
• Time to action: Track how quickly recipients take desired actions after receiving emails

Practical approaches:

• UTM parameters: Add tracking codes to email links to monitor website behavior and conversions in your analytics platform
• Event tracking: Set up tracking for specific actions like downloads, form submissions, or account activations
• Revenue tracking: Connect email campaigns to sales data to understand ROI
• Cohort analysis: Compare the behavior of engaged email subscribers vs. non-subscribers

Start with one business metric: Pick the most important business outcome for your emails (signups, purchases, feature adoption) and track that consistently before adding complexity.

Advanced Metrics Analysis

While basic metrics are visible in your email dashboards, more complex analysis can be performed using Brew’s AI analytics features:

Ask Brew button

Located at the bottom of your email dashboards, this feature allows you to ask specific questions about email performance:

“Why did this email perform better than my previous one?”

“What was the bounce rate for my last campaign?”

“How many people unsubscribed from my newsletter series?”

“What caused the drop in clicks between emails 2 and 3 in this automation?”

Ask AI

Access this from the main navigation menu to explore broader patterns and trends:

“Show me a graph of my open rates over the last quarter”

“Which day of the week gets the best engagement?”

“Compare unsubscribe rates between my welcome sequence and newsletter”

“What’s my average spam complaint rate across all campaigns?”

For comprehensive guidance on using these features, see our Ask AI documentation.

Email Marketing Terms

Essential terms to understand when analyzing your email performance with Brew:

Above the Fold

The portion of your email that recipients can see without scrolling. Critical for placing your most important content and calls-to-action where they’ll be immediately visible.

Automations

Multi-step email flows that are automatically triggered by specific contact actions, behaviors, or timeframes. Used for onboarding new customers, driving product adoption, nurturing leads, retaining customers, upselling customers, and winning back inactive users. In Brew, you describe your automation goal and the AI builds the entire flow with optimal timing and branching logic. Learn more about Automations.

Bounce Rate

The percentage of emails that couldn’t be delivered to recipients. Includes both hard bounces (permanent failures) and soft bounces (temporary issues like full inboxes). Brew automatically handles bounce management to protect your sender reputation.

Call to Action (CTA)

A button or link in your email designed to prompt a specific action from recipients, such as “Download Now” or “Get Started.” Essential for driving conversions. Learn how to optimize CTAs in Campaigns.

Campaigns

One-time emails sent to multiple recipients simultaneously. Perfect for announcements, newsletters, promotions, events, and other standalone communications. With Brew, you describe your campaign goal and the AI generates, personalizes, and optimizes your email in seconds. Learn how to create Campaigns.

CAN-SPAM Act

U.S. federal law that sets rules for commercial email, including requirements for unsubscribe links, sender identification, and truthful subject lines. Compliance is mandatory for U.S. senders. Brew automatically ensures compliance in all marketing emails.

Click-Through Rate (CTR)

The percentage of email recipients who clicked on one or more links in your email. A key indicator of content engagement and email effectiveness. Use Brew’s AI analytics to understand what drives higher CTR.

Contact Properties

Data fields associated with each contact in your audience, such as firstName, lastName, company, or custom fields. Used for personalization through merge tags and audience segmentation in Brew. Learn how to add and manage Contact Properties.

Conversion Rate

The percentage of email recipients who completed your desired action (purchase, signup, download) after clicking through from your email. The ultimate measure of email success. Track conversions using UTM parameters and analytics platforms.

Deliverability

Your ability to successfully deliver emails to recipients’ inboxes rather than spam folders. Affected by sender reputation, content, and authentication. Brew optimizes deliverability through proper domain verification.

Pro tip: Send test emails to yourself, open them, and reply to them. This simple self-engagement signals to email providers that your content is valuable, which can positively impact your sender reputation and deliverability.

DKIM

DomainKeys Identified Mail - an email authentication method that verifies your emails haven’t been tampered with during transit. Helps improve deliverability. Set up DKIM through domain verification.

DMARC

Domain-based Message Authentication, Reporting & Conformance - an email security protocol that prevents domain spoofing and improves deliverability when properly configured. Configure DMARC as part of domain verification.

Double Opt-In

A two-step subscription process where users must confirm their email address by clicking a link after initially signing up. Ensures higher quality subscriber lists and better audience hygiene.

Email Service Provider (ESP)

A platform like Brew that provides email marketing and delivery services, including analytics, automation, and deliverability optimization. Brew serves as your complete system of record for email marketing.

Hard Bounce

An email that permanently fails to deliver due to invalid email addresses, non-existent domains, or blocked recipients. These contacts are automatically suppressed by Brew to protect your sender reputation.

Common causes of hard bounces include:

• Email address contains a typo (e.g., [e-mail])
• Email address doesn’t exist (perhaps the person left the company)
• Email server has permanently blocked delivery
• Domain no longer exists

When an email hard bounces, Brew automatically adds it to your suppression list, preventing future sending attempts to protect your deliverability. You can see the specific bounce reason in your campaign reports by hovering over the bounce status.

Tips to reduce hard bounces:

• Use double opt-in for all new subscribers
• Regularly clean your email list with audience hygiene practices
• Check for common typos in email domains (like gmail.com, outlook.com)

List Hygiene

The practice of maintaining a clean email list by removing inactive subscribers, invalid addresses, and unengaged contacts to improve deliverability and metrics. Learn about audience hygiene best practices.

List Segmentation

Dividing your email list into smaller, targeted groups based on demographics, behavior, or preferences to send more relevant and effective campaigns. In Brew, create targeted audiences and subscription groups.

Merge Tags

Variables that insert dynamic content like contact names, company names, or custom properties into your emails. In Brew, the AI automatically adds relevant merge tags for personalization, and you can add more manually using contact properties.

Open Rate

The percentage of delivered emails that recipients opened. While useful for trends, modern privacy protections make this metric less reliable than clicks and conversions. Use Brew’s analytics to focus on actionable metrics.

Personalization

Customizing email content for individual recipients using data like names, locations, or past behavior. Typically increases engagement and conversion rates. Brew automatically personalizes emails using contact properties and merge tags.

Preference Center

A branded page where subscribers can manage their email preferences and choose which subscription groups they want to receive emails from, rather than unsubscribing completely. Customize your Preference Center in Brew.

Preview Text

The snippet of text that appears after the subject line in most email clients. Often called “preheader text,” it provides additional context to encourage opens. Brew’s AI automatically optimizes preview text for each email.

Sender Reputation

A score assigned by internet service providers based on your sending history, bounce rates, spam complaints, and engagement. Critical for inbox placement. Maintain good reputation through proper domain verification and audience hygiene.

Soft Bounce

An email that temporarily fails to deliver due to issues like full inboxes or server problems. These addresses aren’t permanently suppressed and may receive future emails. Brew automatically manages soft bounces and retry logic.

SPF Record

Sender Policy Framework - a DNS record that specifies which servers are authorized to send email on behalf of your domain. Essential for email authentication. Set up SPF records through domain verification.

Split Testing (A/B Testing)

Testing different versions of an email element (subject lines, content, CTAs) with different segments of your audience to determine what performs better.

Spam Complaint Rate

The percentage of recipients who mark your email as spam. High complaint rates severely damage sender reputation and deliverability. Maintain low complaint rates through relevant content and proper subscription group management.

Subject Line

The title of your email that appears in recipients’ inboxes. One of the most important factors influencing whether your email gets opened. Brew’s AI automatically generates optimized subject lines for all campaigns and automations.

Subscription Groups

Content categories that allow subscribers to choose what types of emails they want to receive from you. In Brew, these replace traditional “lists” and provide more granular control over subscriber preferences, reducing total unsubscribes. Learn how to create and manage Subscription Groups.

Suppression List

A list of email addresses that are blocked from receiving your emails, typically including unsubscribes, hard bounces, and spam complainants. Brew automatically manages suppression lists to ensure compliance and protect deliverability.

Why Brew maintains a suppression list:

• Protects your sender reputation: Continuing to send to invalid addresses or complainants damages your domain reputation
• Improves deliverability: Email providers track how often you attempt to send to invalid addresses
• Ensures compliance: Automatically prevents sending to people who have unsubscribed

Common reasons email addresses are suppressed:

• Hard bounces: The email address doesn’t exist, contains a typo, or the server has permanently blocked delivery
• Spam complaints: Recipients who have marked your emails as spam
• Unsubscribes: People who have opted out of your communications

Brew automatically handles suppression list management, so you don’t need to manually remove these addresses. You can view suppressed addresses in your Audience section and see the specific reason they were suppressed.

Transactional Email

Automated emails triggered by specific user actions containing essential information, such as password resets, order confirmations, or account notifications. These emails typically have 4-5x higher open rates than marketing emails and are sent regardless of subscription status. Learn about Transactional Emails.

Trigger

The starting condition that determines when and how contacts enter an automated email sequence. Brew supports four trigger types: Contact added, A dded to subscription group, Contact updated, and Event received. Learn about Triggers and Events.

Unsubscribe Rate

The percentage of recipients who opt out of your email list after receiving a campaign. Monitored to gauge content relevance and list health. Reduce unsubscribes by using subscription groups and your preference center.

UTM Parameters

Tags added to email links that help track traffic sources and campaign performance in analytics platforms like Google Analytics. Use UTM parameters to measure the business impact of your email campaigns beyond basic open and click rates.

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