When signing up for one of the mailing lists, people
will not necessarily use the same address that is on
their outgoing mail envelope. This results in any
messages they send to the list from their outgoing
address being sent to a queue for approval by the list
I imagine the list admin can then (hopefully) tweak
things to set the allowed incoming address for that
Which would be fine if it got done.
However it appears that that is not happenning, and
messages sent are lost in a spam folder somewhere or
just sent to the bitbucket.