ErrorQuotaExceeded — Quota exceeded

The operation was blocked because it would exceed the user's mailbox quota (storage is full or an attachment is too large). You should not try to write more data until there's free space. Inform the user to clean up their mailbox or reduce attachment sizes. In your app, you might catch this error and pause sending to that account (using /accounts/{accountId}/pause) until the user addresses the quota issue.