Comment Zimbra would work! (Score 1) 204
Zimbra fits your roll perfectly. It's able to scale to the levels of the University I work at, so I'm sure it could handle a 10 man team.
It also supports ActiveSync pushing so it can automatically send appointments to your iPad/iPhone/Android device etc. It also web browser based so no need for a stand alone email client (but you could still use one if you wish).
Also, you can view other peoples Calendars, etc.. and push invites to those people (which my boss does.. she'll push out maintenance calls etc to all of us which automatically get added into our calendar)
www.zimbra.com