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.
Staff received the news this morning when they arrived at work.
BBC News website readers have been getting in touch with their reaction to today's announcement
Chris Ward, London
We all turned up for work in Wimbledon this morning and waited an hour for our mail delivery to arrive before being read the announcement that there would not be one.
We will be paid until the end of the week, but will not be made redundant until the "consultation" is concluded.
So no money, no P45, nothing until we hear from them.
I've loved this job, all one year and nine months of it, but see little chance of it resuming. It's very disappointing.
This feels like limbo.
The news came as a complete surprise, I had no inkling whatsoever.
I am now 64. I got this job when I was 61 so this may be the end of the line in more ways than one, I will have to go back to the job centre to see what they say.
I got to know lots of people on my rounds.
I had a 30-year career before this in the directories business. This was a nice follow-on.
David, Manchester (not his real name)
I was one of the first employees in Manchester. I have worked for them since 2013. I feel gutted and betrayed.
As of this morning I am not entirely sure what will happen. We had a meeting this morning where we were told we were laid off pending a consultation period.
No one knows what that means.
I usually get to work between 0600 and 0630 and by that time there is normally mail to be sorted.
It got to 0700 this morning when the team leader summoned us all and said she had some news and it wasn't good.
This is completely out of blue for the employees. We worked normally this past Saturday.
Grown men were crying this morning, it was heart-breaking.
TNT targeted unemployed people to go and work for them, and paid them the minimum wage. We were all on performance-related pay and the targets were difficult to meet.
It was a brilliant job, we loved it and it was hard to see how the business model could fail.
We will all have to go back on the dole now.
More comments from employees
Nick Nairn, Hammersmith, London: I work as a delivery operative and cycle instructor at the Chiswick depot in West London.
I found out the news this morning when I arrived at work at 0715 and it's fair to say that I was in a state of shock. I didn't expect something like this to happen.
Despite all the criticism, Whistl is a fantastic company to work for and I would hate for something like this to be the end of it.
Sam, Manchester: Found out today that I'm out of a job. Union were not even informed by the company, I had to find out from the news as nobody bothered to let me know.
I work five days a week, and find out that I'm not employed out of the blue. Thanks Whistl!
Charley Newell, London: I've worked for these for nearly five years now, now they want to try and make me redundant?
I feel hard done by and I'm not having it.
Laurence Heyes, Manchester: I have worked for Whistl/TNT post since the very start. I cannot believe I've lost my job - we don't even know what's going to happen.
Comments and experiences of the service
Julius Marstrand, Cheltenham: Despite cherry-picking some of the most lucrative parts of the postal service, including commercial bulk-mailing, leaving Royal Mail to maintain the universal delivery system, even Whistl appears to have been unable to survive in the increasingly fragmented and cut-throat postal system.
TNT was the delivery company that Rupert Murdoch employed to deliver his newspapers from "Fortress Wapping".
Having done its best to undermine both the print and communications workers unions and the public postal service, I have little sympathy for TNT's shareholders, only great sympathy for its underpaid employees.
Wendy Bishop, London: This is the best news I have heard for days. The deliverers can never be bothered to look at the addresses properly and virtually every day I have to re-post mail meant for the other flats.
Why should I trail up the stairs to do their job for them?
I suspect that not only have the deliverers not been given sufficient time to do the job properly, but also that a zero-hours contract doesn't exactly act as a motivator for staff to do a decent job! Are we surprised? Welcome to another five years of the same.
West Londoner, Hammersmith: While I feel bad for the people who will be put out of work, this is great news for the people whose post is delivered by TNT/Whistl.
In the two years I have been living in my flat I have never received a council tax, water or utility bill, my doctors/hospital appointment letters haven't turned up on time, and when I wrote to them to complain they sent the reply by Royal Mail. Their service is a joke I'm glad it's not expanding.