post receipt meaning in English

家产品加工厂证书 --暂时空缺，请各位网友帮忙提供邮政收据
邮政收据

Parcel post receipt evidencing goods condigned to and quoting our credit number
为收货人并注明本证号码的邮包收据
Airway bill or parcel post receipt shall be provided respectively instead of bill of lading )
（如果用火车或者邮寄包裹运输，应该提供空运单或者邮寄收据而不是提单。）
Participants should retain the original post receipt and make constant checks to see if his her submissions are delivered in time
参加人应保留相关的原始邮寄凭据并及时查阅其参赛文件是否被及时送达。