Sheffield is one of the worst places in the country for dog attacks on postal workers, according to the Royal Mail.
It lists the city along with Nottingham, Peterborough, Northern Ireland, Tonbridge, Reading, Leeds and Plymouth as places where postmen and women have reported most attacks while on their rounds.
Around seven attacks a day are being reported nationally, which is a reduction of 10 per cent on the year before, but the Royal Mail is expecting an increase over the summer months, when more dogs are usually out in gardens.
Dr Shaun Davis, Royal Mail's director of safety, said: "As a dog owner myself, I know that the overwhelming majority of dogs are friendly most of the time. But even the most placid animal will defend itself if it feels its territory is being threatened.
"Our postmen and women deliver to over 29 million addresses across the country. We ask them to exercise caution and respect for all family members, including pets, when delivering the mail.
"This summer, we are also appealing to dog owners and their families to help reduce the numbers of attacks, particularly at the door and in the garden."
Dave Joyce, of the Communication Workers Union, said: "Over 2,600 dog attacks on postal workers a year is unacceptable.
"Most dog attacks on postmen and women occur at the doorstep of the dog's owner home. The vast majority of our customers and their dogs aren't a problem but irresponsible and reckless dog owners are.
"The new dog control laws now identify and penalise chronically irresponsible dog owners. One owner was recently fined £8,800 after his dog injured a postwoman as she put letters through the door.
"The penalties can include losing their dogs and jail. Dog owners need to fully understand that their actions usually are the cause of a dog being dangerous and simple precautions can prevent the pain for everyone concerned."