The Business Customer Gateway (BCG) is a portal provided by the USPS that allows businesses to access a variety of postal services online.
Through the BCG, businesses can manage bulk mailings, retrieve data on mail performance, and handle compliance requirements such as uploading USPS Form 1583 forms for your customers.
It serves as a central hub for businesses to interact with USPS services efficiently.
It is mandatory for Commercial Mail Receiving Agencies (CMRAs) to have a BCG account in order to comply with USPS regulations.
USPS provides a full guide to the BCG. You can view it in this link
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