I have noticed that this mailing list seems to be configured in a non-ideal way.
Primarily, the messages are sent from the list address itself, and a reply-to header is inserted for the original sender. This at least often will allow someone to reply to the original sender.
There are a few problems with this. One is that this tends to break messages that have been copied to more than one list, especially for recipients who subscribe to both lists. Admittedly it is better than the all-to-common practice of setting Reply-to to the list itself, which effectively steals all replies from any other recipients or lists that were originally included.
Secondly, however, this kind of violates the intent of the reply-to field, which was intended for the originator of the message to be able to give an alternative address they wish for replies to go to.
I don't know how this list is hosted, and usually this kind of configuration results from an ISP that rejects messages. But, I know a lot of mailing lists are managed with mailman without these problems, so it should be possible to get this working in a more homogenous way.
Lists admins, feel free to contact me if you want any assistance in trying to configure the list better.
Thanks, David