Royal Mail has unveiled plans to trial ditching Saturday second-class letter deliveries which could pave the way for the service to be fully axed.
Almost one million households across the UK will no longer receive second-class post on Saturdays under the trial, which is expected to begin in February.
A phased process will eventually see 1,200 delivery offices across the country offering the service three times a week between Monday and Friday.
First-class deliveries are set to remain available six days a week, with such high-priority post being combined into vans alongside parcels.
Royal Mail is set to be taken over by Czech billionaire Daniel Kretinsky next year under the £3.6 billion sale of parent International Distribution Services PLC (LSE:IDS).
The postal service has repeatedly called for Universal Service Obligation rules, which require one-price letter deliveries on six days a week, to be watered down.
A successful trial would add to its case for the rules to be overhauled, with a consultation expected by regulator Ofcom in the new year.
Letter deliveries have fallen from a peak of 20 billion a year two decades ago to seven billion currently, with a further drop anticipated in the future.