Postal business Whistl - formerly TNT Post - has suspended its door-to-door delivery service in London, Liverpool and Manchester and is consulting 2,000 workers on redundancy.
The move follows a decision last month by potential investment partner LDC not to fund its expansion plans.
Whistl will continue to provide a service, but will revert back to using the Royal Mail for the "final mile".
Shares in Royal Mail rose 3.3% after the news was announced.
Last month, LDC, a division of of Lloyds Banking Group, decided against investing in Whistl because of "ongoing changes in UK postal market dynamics and the complexity of the regulatory landscape".
At the time, Whistl said it would hold back from expansion but planned to continue its existing service.
Whistl said: "Following the announcement from LDC that it would not proceed with the proposed investment... to fund further rollout of E2E [end-to-end] we have now commenced an extensive review of the viability and potential for the rollout of an e2e postal delivery service in the UK."
Courtesy: bbc.co.uk/news