Though Off Topic, certainly there are more issues than just unsubing or NOMAIL: 

1) do they read it or junk it

2) is it delivered at all (many folks forward to non-institutional ISPs, some of which bounce for "spam" or account anomalies)

3) is it delivered in a timely fashion (don't know about you, but I've never heard of a univesity service level agreement wrt. mail operational delivery

4) who is authorized to post (and is anti-spoofing confirmation in force)

5) on an institutional mission critical basis, dealing with bounces, such as 2) i.e., if you are requiring them to receive the message, what are you dong to ensure that the processes are working properly? do you communicate with postmasters about problems? do they respond?

6) ??

LISTSERV sub processing is just one of the cogs in this communications "machine."