I don't know what file it's documented in yet, since I haven't had time
 to carefully review the new release...  The following options (as used
 on the "SET LISTNAME option" command) are mutually exclusive.
 
   MAIL, NOMAIL, DIGEST, INDEX
 
 So you choose what type of delivery service you want from those choices.
 To "turn off digests" you simply choose another delivery type.  The
 frequency of the digests is controlled by list configuration keywords
 and can only be changed by the owner or LISTSERV administrator.  I
 believe the options are "daily" and "weekly" with a "maximum size"
 parameter too.  The frequency and "max size" are not user configurable.
 
 -jj