"J. P. Gilliver (John)" wrote:
In message , Frank Slootweg
[...]
P. S. - I've just read your post that says WM (and the terrible WLM)
_does_ use single files per email (though you call them mbox rather than
file).

Sorry for the confusion. 'mbox' is a *format*, i.e. like PDF is a
format. WM/WLM stores individual messages in .eml files. mbox-format
files can store one or multiple messages. Instead of 'mbox [format]
files', I might say '.mbox files', but there really is no such thing,
because mbox format stems from UNIX, which mainly uses extension-less
filenames.

.eml format is very similar to one-message-per-file mbox format. The
main difference is that the mbox format file should have a "From ..."
line as the first line. For example my response you're referring to has

From franks Mon Sep 17 20:49:58 2018

as it's first line.

N.B. This line should not be quoted by my or your newsreader, i.e. it
should NOT say "From franks Mon Sep 17 20:49:58 2018"

N.B.2. This is NOT the normal 'From:' (i.e. with colon') header, but an
extra *line* (not *header*), which is part of the mbox format, not part
of the posted article.