Uuencode
The 1980s way to mail a binary.
Where it came from
Uuencode ("Unix-to-Unix encode") appeared in the early 1980s to send binaries over UUCP and Usenet, where only text could travel. It wrapped files in begin 644 / end blocks with permission bits.
It predates MIME and Base64 by years. Once email standardized on Base64, uuencode became a historical curiosity — but old archives and Unix folklore still hold it.
How it works
It encodes 3 bytes into 4 characters by adding 32 (space becomes the smallest value). The begin line carries the file mode (e.g. 644) and name; end closes it.
The format is famously fragile: a single corrupted line breaks the rest. UWC still uuencodes and uudecodes it for completeness, entirely offline.