In article <20170731132508.GA22575@xxxxxxx> you write: >One of the best approaches to ensure the long-term preservation of these >archives is to (1) keep them in an open, standard, widely-supported >format -- "mbox" is clearly the best choice Er, not really. See RFC 4155. There are way too many not quite compatible versions of mbox. If I wanted a file format for a multi-file archive, I'd probably use POSIX ustar which is an actual standard. On the other hand, I see that there are rsync-able archives in some mbox variant, so that horse left the barn ages ago. The archives are kind of funky, e.g., the file dnsop/2001-01.mail contains messages from March 1999 through January 2001, and there are empty files 1999-06.mail through 2000-12.mail. R's, John