Quoting Rory Campbell-Lange from 15 May (a Thursday in 2025) at 0640 hours... > > I didn't know that. I see on the man page mutt can save as mbox, MMDF, MH or > Maildir using the -m flag. I couldn't see any docs about saving in the > different mbox formats, which I understand from > https://docs.aspose.com/email/net/email-storage-formats/ to be as follows: > > * MBOXO: > The original format where “From " lines in the email body are quoted > with a > character. > > * MBOXRD: > A variant of MBOXO that further extends the quoting method of “From " > lines. > > * MBOXCL: > Introduced by the “Classic” MBOX variant where each “From " line is > quoted with an ffrom string. > > * MBOXCL2: > A variation of MBOXCL where “From " lines are doubled to distinguish > them.
The "ffrom string" and the "lines are doubled" bits there are gibberish. I wonder if that page is AI slop? MBOXCL uses 'From ' escaping in an irreversible manner, but doesn't do From_ scanning, instead using a Content-Length header. MBOXCL2 uses no escaping, and uses a Content-Length: header My info comes from this historic page, which was the first to document and name the variants that I encountered, and is still my goto reference on the matter. https://web.archive.org/web/20160423115957/http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/mail-mbox-formats.html That page claims that mutt uses MBOXCL type when converting from other MBOX types, whilst other messages in these threads say mutt uses MBOXCL2. My own quick and dirty testing in creating a mbox with a test message with various quoting, and moving messages to a new mbox, looks like it's reliably writing MBOXCL2. .../Nemo
