Our organization is reaching around a 100 email addresses (60 odd user addresses + assorted ones i.e. firstname.lastname@example.org, email@example.com) along with about a dozen email groups.
Currently we are using Google Apps at $50 per email address per year. Right now thats $5,000 a year. At our current rate of growth I'm estimating we may need upto another 50 addresses. Is it worthwhile at this point to switch to an internal email solution (I.e Zimbra?) which could be hosted in an external datacenter, or is it still cost effective to use google apps.
Note we use Atlassian Confluence for our wiki system and Atlassian Crowd for SSO, so Google Apps is offering us little ROI save for the administration burden. (I'll add I am the defacto CTO and am still in process of hiring. We are getting a backend LAMP Developer first and then in six-twelve months a sys admin and network engineer).
I know there can be many debates, ideally if you answer I'm looking for a cost benefit / ROI analysis of the switch (factoring in time to administrate and other such time burdens..)