Storage quota exceeded: Google imposes daily quotas when creating calendar and contact items. This error indicates that Google is preventing the creation of contact or calendar items. This problem will more frequently be encountered when migrating mailboxes containing a large number of calendar or contact data.
Wait an hour and resubmit for migration (Google will "reset" your quota).
If you'd like to proceed with email migration only, please perform the following steps:
1. Select the line item checkbox
2. Select Start > Full Migration
3. Un-check all options **EXCEPT** for Mail
4. Submit your migration pass
This will allow the migration to attempt to migrate mail items only. You can then submit a calendar and contacts migration pass at a later time.