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Use cases → Email operations

Apply labels in bulk to mailboxes via delegation

Apply or update Gmail labels across multiple user mailboxes efficiently using a domain-wide delegated service account.

Who it is forIT admins or automation teams needing to enforce or tidy up labelling across many users.
APIsGmail API
Typical scopesgmail.modify

The problem

Manually managing labels at scale is slow, error-prone, and inconsistent. Delegated automation is the only practical way to guarantee uniform label application or clean-up across hundreds or thousands of accounts.

How it works

  1. Create or select a service account with domain-wide delegation over gmail.modify.
  2. Impersonate each user and ensure the target label exists, creating it if necessary.
  3. Batch process messages using the users.messages.batchModify endpoint to add or remove the label.
  4. Log progress and failures per user for later review.

What changes

Labels are applied or updated across all targeted mailboxes rapidly, with reliable tracking and minimal manual intervention.

The trap in this one. The users.messages.batchModify endpoint accepts up to 1000 message IDs per call, but if any ID is invalid (e.g. deleted in the meantime), the entire batch silently skips that message without raising an error. This leads to inconsistent labelling unless you cross-check the final state. Relying on optimistic batching without verifying post-operation can leave a subset of messages unlabelled, especially during periods of heavy mailbox activity.

Questions people ask

How do I ensure the label exists for every user?

List the user's labels first; create the label if it's missing before applying it, since label IDs differ per user.

Is there a way to undo label application if something goes wrong?

Yes, as long as you track which messages were labelled, you can remove the label using the same batchModify endpoint.

Want this built?

This is a pattern we run in production. We will set up the delegation and build this on top of it — $500 per hour, most of it working the same day.

Talk to us Or read the setup guide

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