Add a format (f) specifier after the archive retrieval command:
where ‘f’ is ‘r’ for RFC1153 format, ‘m’ (mime; default) for MIME multipart/digest with subset of ordered headers, and ‘v’ (virgin) MIME multipart/digest, i.e. with all headers retained from the archive, and ‘n’ (native) the same as ‘v’ except that no threading is performed and messages are returned in numerical order. Under some circumstances, it may be preferable to have a digest in ‘multipart/mixed’. The ‘x’ (mixed) format is identical to ‘m’ except for this header.
For ezmlm-cron(1), just suffix the format code to the digest code.