Regular Saturday letter deliveries on the Isle of Man will end on 19 October, the post office has confirmed.
Deliveries are being cut from six days a week to five in a cost-saving measure approved by politicians in December last year.
A post office spokesman said the change would save £500,000 a year and help “offset the declining letter mail income”.
Parcel and priority mail deliveries will continue.
The Communication Workers Union said it was a “backward step”.
The volume of letters handled by the post office has almost halved over the past decade, dropping from 16 million to 30 million annually.
The organisation made a loss for the first time in its history in 2017-2018.
A union spokesman said it was “a very sad day for a great public service on the Isle of Man”.
He added: “It’s a backward step that people will regret.”