I found the following in the documentation. It may
help.
Receiving Messages in a
Digest
------------------------------
A mailing list can be
configured to bundle sets of posted messages
together into a
collection called a "digest." Each mailing list
can have
several digests configured. The most basic way to change
your delivery class to receive a digest is to use the following
command (substitute the name of a mailing list for
LISTNAME):
set LISTNAME digest
In
addition, there are three digest formats available, MIME, text,
and index. MIME digests cause each message to be included as
an
attachment; this is the most common format. Text digests
have
all of the messages collected into one attachment.
Index digests
list only the table of contents, not any of the
actual messages.
To choose a new digest, add its name to the set
command:
set LISTNAME
digest-mime
Each mailing list can have several digests.
To see details for a
particular mailing list, use the
command
lists-full LISTNAME
As an
example, if a list has three digests (daily, weekly, biweekly),
you can include their names in the set command:
set LISTNAME digest-daily-index
set LISTNAME digest-weekly