# Tracking

Mimeo measures its own opens and clicks rather than trusting the provider's numbers. That's what makes engagement data consistent no matter who delivers your mail — and yours to keep if you switch.

## How it works

At send time, Mimeo rewrites the compiled message in two ways.

| Endpoint                | What it is                                                                                                                                                                                                 | 
|-------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `GET /o/:token`        | The open pixel. Mimeo injects a 1×1 GIF into the message;<br> the mail client requesting that image is what registers an open.                                                                              |
| `GET /l/:token`        | The link redirect. Links in your email are wrapped so clicks pass<br> through your Mimeo, which records the click and then issues a<br> `302` to the real destination.                                        |

Both tokens are generated per send, so a hit identifies the person, the email, and the specific send it came from. You never construct or call these URLs yourself — Mimeo creates them, and the reader's mail client is what requests them.

The redirect happens on your connected sending domain's link host
(`mimeo.yourdomain.com` — see
[Sending domains & senders](/content/docs/usage/domains-and-senders.html)), so a wrapped link is one extra hop on your own domain before the destination. Recipients land where you sent them.

## Bot filtering

A large share of email "engagement" isn't human. Security scanners, spam filters, and link-preview services fetch every image and follow every link in a message before anyone reads it. Left unfiltered, that inflates open rates and makes click data useless.

Mimeo applies two filters.

### Known scanners

Hits from user-agents that identify as known scanning infrastructure are flagged on arrival.

### Click-burst detection

Scanners that don't announce themselves still behave unmistakably: they open everything at once. If **3 or more distinct URLs** from a single sent email are clicked within **10 seconds**, the whole burst is flagged. No human reads an email and clicks four different links in eight seconds.

### What flagging does

Flagged hits are **kept, not deleted**. Specifically:

- They're **excluded from stats**, so your open and click rates reflect people.
- They still **appear in the person's timeline, dimmed**, so you can see what actually happened.

Keeping them matters when you're debugging. "Did that link work?" is answerable when a scanner's successful fetch is still on the record — it's just not counted as a customer clicking.

Because scanner traffic is filtered out, your Mimeo open rate will usually read _lower_ than the same sends measured elsewhere. That's the numbers getting more honest, not engagement dropping.

## Acceptance is not delivery

The send log records that your provider **accepted** the message. That is not proof it reached an inbox. A provider can accept a send and then drop it — most commonly because the address is on the provider's own suppression list — without reporting an error.

The truth about bounces and suppressions reconciles separately: providers report them by webhook as they happen, and a nightly suppression sync double-checks recently-emailed people where the provider supports reading suppressions back.

So when you read a person's record, read the three signals as distinct facts: the send log says the provider took it, suppression state says whether the address is deliverable, and tracking says whether a human engaged. A send that was accepted, is now suppressed, and never registered an open tells a coherent story — the message was dropped.

## What tracking is authoritative for

Your Mimeo's own tracking is the source of truth for engagement. Keep provider-side open and click tracking switched off — your Mimeo's numbers are the ones its features act on, and the ones that stay with you when the provider changes.

Next: [Postmark API notes →](/content/docs/api/providers/postmark.html)