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Every metric you’ll see in Reading analytics, with its formula and how Brew tracks it. For the wider vocabulary, see the Glossary.
This page uses “campaign” in its general email-marketing sense, the way the metrics themselves are defined across the industry. In the Brew product, campaigns live under Emails. See Emails.

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Core Engagement Metrics

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Open Rate

Open rate measures the percentage of delivered emails that recipients opened. Open Rate=Number of emails openedNumber of emails delivered×100Open\ Rate = \frac{Number\ of\ emails\ opened}{Number\ of\ emails\ delivered} \times 100
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.
Open rate shows whether your subject line and preview text earn the click. It’s also shaped by sender reputation and the recipient’s past experience with your brand.
Average open rates vary by industry, but generally:
  • 15-25% is considered average
  • Above 25% is good
  • Above 35% is excellent
Open rates have become increasingly unreliable due to privacy protections and technical limitations:
  • 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
  • Email client defaults: Some clients block image loading by default, preventing open detection entirely
Focus more heavily on click-through rates and conversions as more reliable engagement indicators.

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Click Rate

Click rate, also called Click-Through Rate (CTR), is the share of delivered emails that got at least one link click. Click Rate=Number of unique clicksNumber of emails delivered×100Click\ Rate = \frac{Number\ of\ unique\ clicks}{Number\ of\ emails\ delivered} \times 100 Click rate reflects how engaging and relevant your email content is, and how compelling your calls-to-action are. Strong CTAs with clear value propositions, appealing design, and strategic placement drive higher click rates.
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 click rate and identifies which specific links received the most engagement.
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.

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Conversion Rate

Conversion rate measures the percentage of recipients who completed your desired action after receiving your email. Conversion Rate=Number of people who completed the desired actionNumber of emails delivered×100Conversion\ Rate = \frac{Number\ of\ people\ who\ completed\ the\ desired\ action}{Number\ of\ emails\ delivered} \times 100
Unlike opens and clicks, conversions are tracked in your own analytics platform, not in Brew. Set one up, like Google Analytics, to measure these outcomes.
Conversion rate matters because it measures the business impact of your email campaigns. While opens and clicks are important engagement metrics, conversions represent actual business outcomes.
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 (like Google Analytics) to track these actions
  4. Set up goals or events in your analytics platform to measure completion

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Deliverability Metrics

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Bounce Rate

Bounce rate measures the percentage of emails that could not be delivered. Bounce Rate=Number of bounced emailsNumber of emails sent×100Bounce\ Rate = \frac{Number\ of\ bounced\ emails}{Number\ of\ emails\ sent} \times 100 Bounce rate primarily reflects the quality and hygiene of your contact list. High bounce rates usually mean your list has outdated or bad addresses, not a problem with your content or sending practices.

Hard Bounce

Permanent failures due to invalid addresses or blocked domains

Soft Bounce

Temporary issues like full mailboxes or server problems
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.
If your bounce rate moves toward 2% (20 bounces per 1,000 emails sent), Brew notifies you with steps to resolve it. An in-flight gradual send halts rather than keep going. Keep it as low as you can: bounces damage your domain reputation and the deliverability of the whole platform. Regular audience hygiene is what keeps the rate down.

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Unsubscribe Rate

Unsubscribe rate measures the percentage of recipients who opted out of future emails. Unsubscribe Rate=Number of unsubscribesNumber of emails delivered×100Unsubscribe\ Rate = \frac{Number\ of\ unsubscribes}{Number\ of\ emails\ delivered} \times 100
Unsubscribe rate indicates whether your audience finds your content valuable and relevant to their needs. High unsubscribe rates suggest your content isn’t matching what recipients expected when they signed up.
Most email experts consider an unsubscribe rate below 0.5% to be normal.
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. Unsubscribe Page: When a recipient clicks this link, they’re taken to a branded unsubscribe page where they can opt out of marketing emails.
  3. Immediate Processing: The contact is immediately marked as unsubscribed and Brew updates their status in your audience.
  4. Suppression: The contact will no longer receive marketing emails (campaigns and automations).
Brew automatically handles the entire unsubscribe process for you. Unsubscribed contacts are skipped for campaigns and automations, in line with CAN-SPAM regulations, which distinguish between marketing and transactional communications. Transactional email, an automation sending from a transactional-purpose domain, still reaches unsubscribed contacts because it carries essential information.

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Complaint Rate

The complaint rate is the percentage of delivered emails that recipients marked as “Spam” or “Junk”. Complaint Rate=Number of spam complaintsNumber of emails delivered×100Complaint\ Rate = \frac{Number\ of\ spam\ complaints}{Number\ of\ emails\ delivered} \times 100
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 complaint rate and provides alerts if rates approach concerning thresholds.
A complaint is someone hitting “report spam” in a mailbox like Gmail. It’s different from a bounce, an address that could not be delivered to at all. If your complaint rate moves toward 0.08%, under 1 complaint per 1,000 emails sent, Brew notifies you with steps to resolve it. That threshold sits below the 0.1% Gmail and Yahoo recommend, and below the limits in the Acceptable Use Policy. Sending relevant content to engaged contacts keeps the rate low.

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Automation-specific Metrics

Runs, Succeeded, and Failed describe automation runs, not individual emails. They live with the automation itself rather than in the analytics view. The analytics view logs the send and engagement events those runs produce.
  • What it means: the number of contacts who entered the flow when the trigger fired
  • When it increments: the moment a trigger event fires for a matching contact
  • What it means: contacts who completed every step in the flow, including all Wait nodes
  • Why it lags Runs: a flow with Wait nodes takes days or weeks to complete, low Succeeded vs Runs is normal if the flow launched recently
  • What it means: contacts whose run stopped mid-flow due to an error
  • Common causes: hard bounce, missing required payload field, filter that couldn’t evaluate
  • What to do: open the automation’s run history and click into the failed run to see the specific error, or click any of its events in analytics and use View run