Hi, I think, mutt should not overwrite an existing file of mbox format while the user wants (as an error) to save an attachment to a file; there is a warning question about append/overwrite/cancel, but mutt could detect on overwrite that the target is a mbox and should deny it or raise an additional last warning.
Thanks matthias -- Matthias Apitz | /"\ ASCII Ribbon Campaign: www.asciiribbon.org E-mail: g...@unixarea.de | \ / - No HTML/RTF in E-mail WWW: http://www.unixarea.de/ | X - No proprietary attachments phone: +49-170-4527211 | / \ - Respect for open standards