Colin Blaney, from Gorebridge, Midlothian, was targeted by mail bosses after cards were opened at the North Berwick sorting office in East Lothian.
Test packages were placed into the mail system in an effort to catch the thief, and each packet was subsequently opened by the mail worker.
At Haddington Sheriff Court earlier this week, Blaney, 36, admitted to intentionally delaying or opening a postal packet by opening a number of parcels and stealing an item of mail between July 26 and September 26, 2012.
Solicitor Elaine Clancy said her client only opened the mail to find out who the sender was as he claimed the letters were “undeliverable”.
Sheriff Braid ordered Blaney to carry out 300 hours of unpaid work in the community.