Thieves emptied the Featherston mail box outside the Featherston Post Shop on Saturday night.
Police say they have recovered some damaged and undamaged mail, but are certain items of value, such as cheques or cash, have been taken.
"Anyone who has placed mail containing cheques in the mail box outside the Featherston Post Office during the Easter weekend should notify their bank and the receiver immediately."
The recovered mail will be sent as soon as possible.
Police encourage anyone who has posted mail in the Fitzherbert Street Post Office Box to call NZ Post on 06 308 8000.
