On Thu, Jan 29, 2026 at 12:06:36PM -0500, Derek Martin wrote:
https://www.jwz.org/doc/content-length.html
...
Essentially the only safe way to parse that file format is to consider all lines which begin with the characters ``From '' (From-space), which are preceded by a blank line or beginning-of-file, to be the division between messages. That is, the delimiter is "\n\nFrom .*\n" except for the very first message in the file, where it is "^From .*\n".
That is the Berkeley variant of mbox that I described earlier. On read, it recognizes an mbox From_ line only after an empty line (or at beginning of file); on write, it does ">From " escaping of a message line only if it's preceded by an empty line.
The original mbox, from 1974, escapes every message line that starts with "From ", and recognizes an mbox From_ line anywhere, not only after an empty line. That's the best-known variant of mbox, and many implementations still do that.
That piece by Zawinski does not acknowledge the existence of original mbox.
