Written and first recorded by Shuggie Otis (1971).
Hit version by The Brothers Johnson (US #5/R&B #1/CAN #8/UK #35 1977).
From the wiki: “Shuggie Otis, son of famed songwriter (‘Willie and the Hand Jive’), bandleader and disc jockey Johnny Otis, wrote the song for a girlfriend who used strawberry-scented paper when she wrote letters to him. Otis recorded it for his 1971 album Freedom Flight. George Johnson of the Brothers Johnson was dating one of Otis’ cousins at the time when he came across an early pressing of the album. The Johnsons recorded ‘Strawberry Letter 23’ for their 1977 album Right on Time, which was produced by Quincy Jones.
“The Brothers Johnson recorded the song in a funkier, more dance-oriented vein than the original Otis version. Their rendition hit the Hot 100 and peaked at #5 and reached #1 on the Soul Singles chart in 1977. Studio guitar player Lee Ritenour recreated Otis’ original guitar solo for the Brothers Johnson recording. The initial issue of the promotional single was packaged in a strawberry-scented sleeve. A later issue of 12″ singles were pressed on red strawberry-scented vinyl.”
The Brothers Johnson, “Strawberry Letter 23” (1977):