The incident happened at Holybourne Post Office in London Road at 6.08am on October 7. A man was arrested and charged in connection with it.
A Hampshire Constabulary spokesperson said: “We are keen to hear from anyone who has CCTV or dashcam footage in the area from 6am to 6.30am on October 7. We are particularly keen to hear from anyone with footage showing a man wearing an orange hoody and riding a bicycle.”
Anyone with information can call 101, quoting reference 44210402282, or call Crimestoppers anonymously and free on 0800 555111.