Failure Log: Duplicate Emails Caused by Zapier Retries
Failure Log: Duplicate Emails Caused by Zapier Retries
This failure usually starts with a sentence like:
“We are not sure why, but some people received the same email twice.”
Sometimes it is three times. Sometimes more.
The automation is still running.
It is just no longer trustworthy.
A Zapier workflow retried a failed step.
The retry succeeded.
But nothing prevented the action from running again.
- Duplicate emails sent to clients
- Duplicate Slack or CRM notifications
- Confusion about what had already been handled
- A growing fear of turning the automation back on
Nothing crashed. Nothing alerted anyone.
Zapier retries steps automatically when something fails.
This is helpful, but dangerous without safeguards.
If the workflow does not explicitly track:
- What has already been processed
- Whether an action already happened
Then retries become duplicates.
This is not a Zapier bug.
It is missing idempotency.
Why This Was Hard to Spot
Retries happen after the trigger.
Logs show “success”.
The failure mode is not technical.
It is logical.
- Introduce a unique processing key
- Store state outside the Zap
- Prevent actions from running twice
- Move critical logic into a system that can enforce memory
Sometimes this means Apps Script.
Sometimes it means redesigning the workflow.
Designing for failure, not success.
Retries should be safe by default.
This post documents a real automation failure mode. Similar failures often appear under labels such as duplicate actions, retry storms, and missing state.