We use (and implement) Google Apps and we are extremely satisfied with it.  Personally, I believe that nonprofit organizations (and businesses) should focus on their mission and not on maintaining their servers. Also, your data is much more secure in the cloud than what lives on a tower under your desk. 

Tal

Disclosure: I love the cloud :)

Some organizations are so heavily regulated by HIPPA that using something like Google Apps (ESPECIALLY with Google's blatant disregard for privacy issues) just will not cut it in my opinion.

There are conditions regarding privacy where you need to ascertain how securely things like your email are being handled. Anyone paying any attention is already aware of Google's history with user data. With that knowlege, if you are using Google Apps for confidential information such as email subject to HIPPA regulation then you are likely opening yourself up for serious legal trouble.

We have all read about Google's security and confidentiality breeches. Are you willing to put your organization's data into their hands? While your org's data may not be subject to the stringent regulations of some other org's, the risk may very well be worth it. For my org, it is not a viable alternative.

To get back to the question, our servers are situated off-site, yet completely within our control. There are monster generators and UPS systems in place. While certainly not a realistic alternative for most non-profits, it is par for the course in ours.

In one of my orgs we use a third party provider to host email and use outlook to retrieve the email.  Our key staff have smart phones that also access the email account, this provides service incase the office is unavailable.  There is also web based access to the email service.  We do have a mini crisis when email doesn't get through or when our provider is blacklisted. 

Another org has the email hosted outside our facility, and I use exchange to pull the mail from the external host and then BES to push mail to the phones and Outlook for our key users.  The rest of the users use the Webmail or pop interface.  When the BES server has issues it can become very frustrating for the users and their world comes to a standstill.  If Exchange or our server is down, then can at least monitor and respond through the webmail interface, but if Exchanged has grabbed the message, it is locked away until the server is back on line.

For no to low cost options this has worked well for the orgs with out spending more $$$,

I haven't seen reasonable discussion on archiving requirements for non health care non profits, in regards to  Sarbanes–Oxley and our auditors have not been concerned about that with us.

Dave

Our org is also governed by HIPPA, so we host our own email and are implementing a secure messaging solution to allow patient/doctor and/or nurse communications.  Our org is very anti-cloud as they feel that our mission is being met in-house. 

As far as the original question, we have our Exchange server in our climate controlled server room in an APC Infrastructure rack with a 30 minute battery backup.  We have wanted to get ermergency generators, but the building's current wiring would make that cost-prohibitive.  Our office hardly ever loses power.  I can think of twice off the top of my head in the 7 years that I have been working here.  

Gary