It is possible to use the wildcard symbol to limit postings to @uiowa.edu addresses. The following option in the list header configuration will limit postings to the list owner and anyone with a @uiowa.edu address:

Send= Owner,*@uiowa.edu,Confirm

You can also restrict sending using the Service keyword.

Service= uiowa.edu

Service= *.example.com

Lsoft Video Tutorial -- Restrict an email list to subscribers from a certain domain only