I have the following set to YES for Digest mode.
*Set Digest Mode*
If you turn digest mode on, you'll get posts bundled together (usually one
per day but possibly more on busy lists), instead of singly when they're
sent. If digest mode is changed from on to off, you may receive one last
digest.
Off
On
However, I still get several "Digests" a day, recently. I am a little
surprised at that. Other groups I am subscribed to do not do this.
If Mailman has a setting that determines when to send a digest, and it set
really low, possibly to impress people like me that the group is a live and
well and saying a lot of encouraging things, well ... it is working. But we
may not need to have so many digests per day.
It gets hard to digest (smerk).