The license comes after a drought of applications and has reignited Postcomm's hopes for more small businesses to follow suit and apply for a licence.
Sarah Chambers, chief commissioner of Postcomm, said: "New companies entering the market bring with them innovation and creativity. They challenge the way services operate and help change the attitude of Royal Mail. Growing competition has already sharpened up the industry and we hope this will continue to develop through new ideas."
The licensing process has recently changed to make it easier and cheaper for small companies to register. Once licensed, a postal operator can collect, sort and deliver mail, although most rely on Royal Mail for the final mile delivery.
Post 123 is registered as a sole trader. The company intends to provide a weekly bulk delivery to 2,000 addresses across three Manchester post codes.