ezmlm list may be set up with a digest function. This is basically a second address database used to send out “digests”, ordered collections of messages sent to the main list. Usually, a “digest” is sent out every other day. This is very convenient for users who want to follow a list, but not participate in the discussion. A digest is sorted, so it's easy to read what interests you. Thus, the digest for ‘email@example.com’ would be called ‘firstname.lastname@example.org’ and you would mail ‘email@example.com’.
Simple ezmlm-idx lists test if the conditions for a digest are met whenever a message arrives. Thus, the digests do not arrive at a specific time, but rather approximately every two days, or more often if there is a lot of traffic.
On some mailing lists you are a subscriber, and as a subscriber, you can choose to receive the messages individually or as a digest. With ezmlm, you can subscribe to the “list” for individual messages, or to “list-digest” for digests. Some people prefer to subscribe to both: They can keep up with a discussion if they like, but if they have too little time they can just delete the individual messages and read the “threads” that interest them. To switch from being a “list” subscriber to being a “list-digest” subscriber, simply subscribe to the digest and unsubscribe from the main list. You will still be able to post to the main list.
With some mailing list managers, the digest is edited by a human. ezmlm digests contain each message as it was sent out by the list (apart from having many less informative headers removed). No editorials, no missing messages. The messages are ordered by subject (or “story” or “thread”) and within each subject by arrival time. First in the digest is a table of contents with subjects, message numbers, and authors. Messages are enclosed as attachments so that a MIME-capable mail reader will allow you to see them as individual messages. This way, you can easily follow-up on a post even from the digest. The owner may chose to use a non-MIME single message format instead. This is most often done on old lists where the subscribers are used to that format and unaware or due to deficient mail readers unable to appreciate the advantages of the MIME format (Pegasus Mail and Mutt are free programs that do a good job).
The digest of a list “list” is called “list-digest”, and the commands are the same as for the main list. Thus, to subscribe to ‘firstname.lastname@example.org’ (the digest of ‘email@example.com’) send a message to: ‘firstname.lastname@example.org’, or to subscribe the address ‘email@example.com’ send to: ‘firstname.lastname@example.org’. Of course, ezmlm will send a confirmation request, and then a message notifying the user that s/he is a subscriber. If the list owner has chosen to restrict posts and archive access to subscribers, digest subscribers are automatically given the same privilege.