Postal workers took almost three months to send a letter just 12 miles, it has been claimed.
The letter, addressed to Millie Coppard, 97, was from the Royal Sussex County Hospital in Brighton, giving the details of a hospital appointment.
The letter was posted on October 26, but was only received by Mrs Coppard on Monday (Jan 24).
By the time the letter arrived, Mrs Coppard had missed her November 9 appointment to have her pacemaker checked.
Mrs Coppard’s son Leslie, of School Field, Barcombe, near Lewes, said: “The letter was for my mother because I deal with her correspondence.
“She is 97 and has a pacemaker and had an appointment to check it was operating properly.
“Luckily it wasn’t an emergency, but it is still something you would want to know about."
However Mrs Coppard’s three month late hospital appointment letter is thought to be the most delayed piece of correspondence in the county.
The Royal Mail yesterday insisted there were no delays in the network in October.
A Royal Mail spokesman said: "Without examining the item in question, it is difficult to explain what may have happened but it is unlikely that the letter has been in our system for that length of time. It is most likely that it has been put back into the system and subsequently delivered."
Have you received a letter delayed even longer? Call 01273 544519.