I think that many users might benefit from a plugin
that adds the capability of a shared address book.
For example, a business that is using SquirrelMail
might want to be able to create a shared address book
that will contain contact info for all the employees,
allowing them to easily look up the address for anyone
else in the company. Users should still have access
to their own personalized address books. However,
they would also have a link to a shared address book
that would only be changed/maintained by a system
admin. I am currently using SquirrelMail in a
university environment, and this would be a great
feature for faculty (and possibly students).