Example: Each periodic check with the accompanying Financial Institution Statement shall be considered to be a legally sufficient answer. Where legal process has been processed but no money was deducted, (for the reason of insufficient pay, prior garnishment in force, etc.) the mailing label or other written response shall be a sufficient answer. Where the Postal Service sends a check or mailing label, no further action will be required (such as a cumulative report or notarized statement.) Documents which are defective with respect to service, lack of legal sufficiency, failure to properly identify the employee, or other reason, do not require a response or an answer but if the Postal Service chooses to act in any way, such as to return the document, that act shall be a sufficient answer.
39 C.F.R. §491.6