Duplicate automated emails can come from multiple triggers, repeated processing of the same event, overlapping executions, or a retry after an uncertain send. Do not assume that deleting one visible trigger proves the entire problem is solved.
Map the actual executions
Record the function, event source, execution times, and effective account. Check the project’s trigger list and whether another user created a trigger for the same workflow. Google’s installable-trigger guide explains that these triggers run under their creator and are not all visible from another user’s account.
Also inspect whether the function is invoked manually or by another scheduled process. Keep the investigation limited to the relevant workflow instead of disabling unrelated notifications across the organization.
Protect against overlapping and repeated work
Use a durable business identifier for each intended email and check its processing state before acting. A lock can prevent two executions from modifying shared state simultaneously, but a lock alone does not remember that an earlier execution already sent the message.
Track a requested, confirmed, failed, or uncertain outcome. If a process stops between sending and recording success, the next run should reconcile that uncertainty rather than automatically sending again.
Retest with one controlled event
After removing the confirmed duplicate trigger or correcting event handling, run a harmless test with one approved recipient. Verify the execution record and the received message. Then test the same event again to confirm the workflow handles it as intended.
Keep useful logs with operation references and sanitized results, not full message bodies or tokens. Do not ask recipients to forward every private message as a substitute for execution evidence. Resume normal volume only after both trigger configuration and repeat-processing behavior have been checked.
Browse Gmail & Google Account help
References
- Installable Triggers | Apps Script | Google for Developers
- Class LockService | Apps Script | Google for Developers
- Logging | Apps Script | Google for Developers
Reviewed against the linked official product guidance on November 3, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.