The MBMAKE command reads zero or more mail message files, and writes them out, concatenated in "mboxrd" form, to its standard output.
wildcards is a search wildcard specification. All files matching the specification are read and processed.
MBMAKE makes no modifications to message content, except to encode the
message as per the file format and (optionally) to add a
Received: header. In particular, note that any IMAP flag and
UID data for a message, as stored in
a standard format mail directory,
are lost by this conversion process.
Received:header to each message that it processes, tracing its path through MBMAKE.