1. Symptom
During an email migration to a Google Workspace mailbox, the migration fails for specific users. When reviewing the user's trace file, you find the following error message repeated:
400 Invalid label: {LABELID} (invalidArgument)
This error indicates that CloudM Migrate is attempting to apply a label to an item, but the corresponding label no longer exists in the destination user's Gmail account. As a result, email items for the affected user may fail to migrate.
2. Cause
The most common cause for this error is that the end user has renamed or deleted a label in their destination Gmail account while the migration is in progress.
When the migration begins, CloudM Migrate creates the necessary labels in the destination mailbox based on the source folder structure. If a user modifies or deletes one of these labels before all items assigned to it have been migrated, subsequent attempts to use that label will fail, triggering the "Invalid label" error.
3. Resolution
To resolve this issue, you must re-migrate the failed items after ensuring the user understands not to modify their labels.
Step 1: Advise the End User
Communicate with the affected user and instruct them not to rename, move, or delete any folders or labels in their new Google Workspace mailbox until the migration is fully complete.
Step 2: Run a Delta Migration
A Delta migration will identify and migrate any items that were missed during the initial pass.
- In the CloudM Migrate interface, select the user(s) who experienced the "Invalid label" error.
- Initiate a new migration pass, ensuring that only Email items are selected. This will act as a Delta migration.
- CloudM Migrate will re-create the missing labels and migrate the remaining items correctly.
Important: Running a Delta pass will not create duplicate items. It will only process and migrate items that do not already exist in the destination mailbox.
4. Prevention
To prevent this issue from occurring, it is best practice to include the following instructions in your pre-migration communications to end users:
"Once your migration begins, you will start to see new emails and labels (folders) appearing in your new mailbox. Please refrain from deleting, renaming, or organizing these new labels until you receive final confirmation that your migration is complete. Modifying labels during this process can cause parts of your migration to fail."