Postmen and women are changing their delivery routes around Eastwood.
Royal Mail said changes were being implemented because fewer letters were being posted, and because the service needed to invest in some equipment to carry heavier parcels more safely.
The service will phase the changes in over the next four weeks.
A company spokesman said: “Royal Mail will continue to deliver in the morning and many customers will continue to get their mail by lunchtime.
“The time customers receive mail will depend on where they live. This may be later or possibly earlier than current delivery times.”