The group playing is divided into two groups – typically a girl group and a boy group. One group goes into another room, such as a bedroom, which is called "the post office". To play, each person from the other group individually visits "the post office". Once there, they get a kiss from everyone in the room. They then return to the original room.
Once everyone in the first group has taken a turn, the other group begins sending members to the first room.
In the variation "Postman's Knock", one person chosen by a group to be the "postman" goes outside and knocks on the door. Another person is chosen by the rest of the group to answer the door, and pays for the "letter" with a kiss. Then another person is chosen to be postman, etc. The game has many variations. In some versions, playing cards are used to select which people get to be postman and which get to be answerer in turn.
In the variation "Pony Express", the "Post Office" is a closet or it is in some other dark room. The game is played the same, but can become more intense.
In Sweden, the game is referred to as ryska posten ("Russian mail/post office").
In Laura Ingalls Wilder's autobiography, Pioneer Girl, she lists games played at teenage parties, including "Postoffice" and "kissing games".
Published in 1929, Is Sex Necessary?, by James Thurber and E. B. White, refers repeatedly to Post Office, and to the possibly similar party game Pillow. (For example, see p. 43 and pp. 49–50 of 1964 Dell edition, copyright 1950.)
In the 1932 film Huddle, a mixed group of college students in high spirits are talking on a train. One of the young men says, "Let's play post office." One of the young women remarks, "That's a kids' game!" The young man replies, "Not the way I play it!" The same gag (which may not have been original even then) is often used subsequently, for example in the Three Stooges short, Three Little Pigskins (1934) and in the 1941 Abbott & Costello movie Hold That Ghost. The joke was a recurring joke by Abbott and Costello. The joke has been used even in more recent times; in the 2013 movie "Gangster Squad", (Ryan Gosling's character uses it on Emma Stone's character).
In the 1932 film The Purchase Price, Barbara Stanwyck and George Brent, are greeted during their honeymoon by friends of the groom, who are there to help celebrate the recent nuptials — and a reason to partake in adult beverages — while playing a spirited game of Post Office.
In 1936 in the Three Stooges episode "A Pain in the Pullman" when the stooges are being kicked out of the star's drawing room, Curly says "I thought she wanted to play post office!"
In the story "Three Hours Between Planes" by F. Scott Fitzgerald (written in 1939 and published in 1941) post office is mentioned as a game that can cause terrible jealousy among children.
In the 1941 movie Ridin' on a Rainbow, Gene Autry rescues a girl from the river. After returning her to her stateroom on the riverboat, a sailor who followed them in states "Let's get out of here before they start playing post office."
"Docks of New York", a 1945 East Side Kids film, Huntz Hall questions Leo Gorcey about what an older well-dressed man would've been doing prowling in the back alley carrying a large knife. Scratching his head while trying to unravel the mystery, Leo replies, "He wasn't playin' post office".
A 1954 television episode of The Jack Benny Show with Fred Allen guest-starring, Benny is surprised by Allen hiding in a closet. When Benny demands to know what Allen is doing in the closet, Allen says, "Playing 'post office.' Kiss me!"
In a 1954 episode of The George Burns and Gracie Allen Show in which Gracie Allen runs for city council, Gracie speaks to the chief of police. Near the end of the conversation he shakes her hand and says "It's been a real pleasure". Gracie replies, "If you think shaking hands is a pleasure, then you've never played Post Office."
In a 1957 episode of Leave it to Beaver "Party Invitation", Beaver goes to an all girl party. One of the girls suggests playing post office.
In his unfinished novel Answered Prayers, Truman Capote writes: "Kissing her, according to Dill, was like playing post office with a dead and rotting whale: she really did need a dentist."
In a 1967 episode of the sitcom Bewitched entitled "I Get Your Nannie, You Get My Goat," Darrin's boss, Larry Tate, disapproves of Darrin and Samantha's kissing in plain view on a patio at a business function for an important advertising client. Insinuating that it could be viewed as unprofessional and therefore embarrassing, Mr Tate says, "Cut that out. What if somebody sees you?...The somebody I'm talking about, Darrin, is Roy Chappell of Chappell Baby Foods. I want to steer him out here so he can meet you and we can sew up the account. And I don't want him to catch you playing post office".
In the 1968 movie Yours, Mine and Ours, Frank, played by Henry Fonda, is on a date with a younger free-love hippie. The date is interrupted by Helen, played by Lucille Ball. While Frank and Helen commiserate over the problems they have with their respective children, the hippie says, "Why don't you drop me off at the exit, then you two can play post office!"
In an episode of I Love Lucy called "The Charm School" (aired 25 January 1954), Ethel mentions that Fred suggested they play post office the previous night when a beautiful guest arrived at their dinner party.
In The Andy Griffith Show (2nd year) episode called "Bailey's Bad Boy", Barney mentions playing "2-handed post office" at the end of the show.
In the 1981 Are You Being Served? Christmas special, "Roots?", in discussing Mr. Grace's upcoming birthday, someone mentions Postman's Knock, which prompts Mrs. Slocombe to recall, "Me and Mrs. Axleby played Postman's Knock on my birthday last year!" Mr. Klein remarks, "Aren't you both a little old for Postman's Knock?" Mrs. Slocombe smiles coyly and says, "The postman didn't think so!"
In Osa Johnson's 1940 autobiography, "I Married Adventure," she writes that her grandmother "was my self-constituted chaperone from the moment she had witnessed a game of kiss-the-pillow at one of my birthday parties..." (p. 71)