Two men were arrested on suspicion of affray after a fight broke out at Sudbury Post Office.
Police were called to the post office in East Street at around 9am on Thursday after receiving a call from staff.
A 29-year-old man from Sudbury and a 30-year-old man from Chelmsford were both arrested.
A spokeswoman for Suffolk Police said: “We were called after reports that two men had assaulted each other. Both men were arrested at the post office.”
The Sudbury man was released on police bail to attend Bury St Edmunds Police Investigation Centre on December 27, pending further inquiries.
The other man is due to answer bail on November 29.