If undelivered, please return to sender.

若无法投递，请退还寄信人。

youdao

To ensure mail items be duly received by the department, and to avoid unnecessary delivery delay (e. g. return to sender), please pay sufficient postage before Posting mail items to this department.

为确保本署能妥收邮件，及免却不必要的派递延误(例如，退回寄件人)，请切记投寄邮件前贴上足够邮资。

youdao

To ensure mail items be duly received by the department, and to avoid unnecessary delivery delay (e. g. return to sender), please pay sufficient postage before Posting mail items to this department.

为确保本署能收妥邮件，并免却不必要的派递延误(例如退回寄件人)，在投寄邮件前，请切记贴上足够邮资。

youdao