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Documentation Index

Fetch the complete documentation index at: https://docs.lettr.com/llms.txt

Use this file to discover all available pages before exploring further.

Once a campaign starts sending, Lettr tracks engagement at two levels: aggregated counts for the campaign as a whole, and individual events for every recipient. Both update in real time as recipients interact with the email. This page covers what metrics are tracked, where to find them, and how to interpret the data after a campaign sends.

Where to See the Data

Every campaign has a Show page (open any campaign from the Campaigns list). It’s the single place to view delivery progress, engagement metrics, the activity feed, and the unsubscribe summary. The page polls live while a campaign is sending and for a window afterward, so you can watch the metrics propagate. You can also compare several sent campaigns side by side by selecting them from the Campaigns list and opening the comparison panel.

Aggregated Metrics

Lettr tracks nine metrics for every campaign. They’re shown as tiles at the top of the Show page.
MetricWhat it counts
InjectionsEmails accepted into the delivery pipeline. Roughly your total recipient count.
DeliveriesEmails successfully accepted by the recipient’s mail server. The baseline for everything else.
BouncesEmails that couldn’t be delivered (permanent failures). Both immediate bounces and out-of-band bounces (rejected after acceptance) are counted.
Spam complaintsRecipients who marked your email as spam in their inbox.
OpensTotal opens across all recipients (so one recipient opening twice counts as two).
Unique opensDistinct recipients who opened at least once.
ClicksTotal clicks on links in the email.
Unique clicksDistinct recipients who clicked at least once.
UnsubscribesRecipients who clicked the unsubscribe link or used their mail client’s unsubscribe button.
Use unique opens and unique clicks for engagement rates — they’re what people usually mean by “open rate” and “click rate”.

How Engagement Is Detected

TypeHow Lettr measures it
OpenA tiny invisible image in the email is loaded when the recipient views the message
ClickLinks in the email are rewritten to route through Lettr’s tracking domain, which logs the click and immediately redirects to the destination
BounceThe recipient’s mail server explicitly rejects the message
Spam complaintThe recipient’s mail provider notifies Lettr through a feedback loop
UnsubscribeThe recipient clicks the unsubscribe link in the email or uses their mail client’s built-in unsubscribe button
Open tracking depends on the recipient’s client loading images. Mail clients that block images by default (some corporate clients, privacy-focused users) will show as non-opens even if the email was read. Open rates tend to slightly under-count in practice.

Per-Event Activity Feed

Below the metric tiles, the Show page has an activity feed listing every individual event that occurred during the campaign. Each event includes:
  • Event type (injection, delivery, bounce, open, click, spam complaint, unsubscribe)
  • The recipient’s email address
  • Timestamp
  • For bounces: the bounce class and reason
  • For clicks: the URL that was clicked
  • For some events: the recipient’s user agent
You can filter the feed by event type to focus on specific behavior — for example, viewing only bounces to diagnose deliverability issues, or only clicks to see what links are driving engagement. The feed is paginated and uses cursor-based navigation, so you can step through even very large campaigns without performance issues.

30-Day Window

Per-event data is available on the Show page for 30 days after the campaign sends. After that, individual events are archived to a downloadable file (see below) and the live feed is no longer populated for the campaign. The aggregated metrics (tile counts) are kept permanently — only the per-event activity feed has the 30-day window.

Real-Time Updates

While a campaign is Preparing or Sending, the Show page polls every few seconds to update progress and metrics. After the campaign reaches Sent, polling continues for roughly 10 minutes to capture the burst of early engagement, then stops. Refreshing the page after that fetches the latest metrics. You can return to the page later — metrics keep updating in the background even when you’re not watching.

Bounce Rate Warning

The Show page highlights campaigns with a bounce rate of 10% or higher with a visible warning. A bounce rate that high is a strong signal that:
  • Your audience contains many stale or invalid addresses
  • Your sending domain authentication may have issues
  • You may be hitting deliverability problems that will affect future campaigns
If you see this warning, audit your audience before sending more campaigns. See List Hygiene for cleanup guidance.

Unsubscribes

When a recipient clicks the unsubscribe link in a campaign:
  1. The contact’s status changes to unsubscribed in your audience
  2. The unsubscribe is counted toward the campaign’s unsubscribe metric
  3. The contact is automatically excluded from all future campaigns
Unsubscribes are permanent until you manually re-subscribe the contact (which you can do from their profile if they ask to be re-added).
A small unsubscribe rate is normal and healthy — recipients self-selecting out of your list improves engagement for the ones who stay. A sudden spike (more than ~0.5–1% of recipients on one campaign) is worth investigating — it usually points to content that didn’t match expectations or an audience that was added without clear consent.

Archived Events

About 28 days after a campaign sends, Lettr archives its per-event activity to a downloadable CSV file. The archive includes every event captured during the 30-day window — every delivery, open, click, bounce, complaint, and unsubscribe — with timestamps, recipient addresses, and detail fields. To download the archive, open the campaign’s Show page after the archive is ready and click the archive download option. Lettr generates a one-time download link valid for 1 hour and sends it to your email. The archive is useful for:
  • Long-term auditing and compliance records
  • Importing campaign event data into your own analytics tools
  • Investigating delivery issues for older campaigns
Aggregated metrics remain visible on the Show page indefinitely, so you don’t need to download the archive just to see the campaign’s open or click rates.

Comparing Campaigns

To see metrics for several campaigns side by side, go to the Campaigns list, select the campaigns you want to compare (use the checkboxes), and open the comparison panel. The comparison view shows the same metric tiles for each campaign next to one another, making it easy to spot trends like “the campaign with the AI-generated subject had a 3% higher open rate” or “the Tuesday send had fewer unsubscribes than the Saturday one”. Only Sent campaigns appear in the comparison.

Reading the Metrics

A quick guide to interpretation:
MetricHealthy rangeWhat it tells you
Delivery rate (deliveries / injections)98%+How well your audience and sender authentication are working
Bounce rate (bounces / injections)Under 2%Audience freshness; above 5% needs attention
Spam complaint rate (complaints / deliveries)Under 0.1%Whether content and consent are aligned with expectations
Open rate (unique opens / deliveries)15–30%+Subject line and sender recognition
Click rate (unique clicks / deliveries)1–5%+Whether content engaged recipients enough to act
Unsubscribe rate (unsubscribes / deliveries)Under 0.5%Whether you’re meeting recipient expectations
These are general benchmarks — every audience and industry has its own norms. The most useful comparison is always against your own historical campaigns.

Next Steps

Best Practices

Improve open and click rates over time

List Hygiene

Reduce bounce rates with audience cleanup

Audience

Grow and organize your audience

Sender Reputation

Protect your long-term deliverability