More than 500 jobs could be lost in the Midlands if Royal Mail's cost-cutting plans are approved.
The company is planning to close the Leicester Mail Centre and downgrade the Derby and Worcester sites to delivery offices.
Leicester's mail processing would move to Northampton, Derby's to Nottingham and Worcester's to Birmingham.
A spokesman from Royal Mail said he was confident the company would be able to avoid compulsory redundancies.
Royal Mail's senior external relations manager, Richard Hall, said he hoped the reduction in posts could be achieved through voluntary redundancies, redeployment and natural wastage.
Mark Greenhill from the Communication Workers Union (CWU) said staff were disappointed about the news.
"We had an inkling as union reps that they were going to shut us [Leicester] down but it came as a great shock to the postmen and women who came in this morning and were told the news.
"We have a meeting next week and will discuss the next steps."
The plans are subject to a consultation period which should finish by the autumn.
Derby would lose 182 posts, Leicester 280 and Worcester 97, out of a Midlands workforce of 17,500.
Paul Jobling, regional operations director of Royal Mail Midlands, said: "Royal Mail's modernisation programme, which is vital to ensuring a successful future for the letters and parcels business, depends on having the right number of people in our business as well as deploying the right technology and equipment."
Royal Mail said the number of items posted each year in the Midlands had fallen by more than 400 million since 2006.