Here's what we've discovered so far about alternate email services.
Many libraries are going with 1&1 hosting, http://www.1and1.com/, which is what's powering the email accounts SEO is now going to be providing to SEO libraries.
The state email hosting service that state agencies use will not be a good fit for libraries, as the price per month (pretty high) includes many services aimed at state agencies, which drives up the cost per user per month.
Office 365 is what powers the state mail service, many library email accounts, and includes an online version of Microsoft Office for each account at $5/month. http://products.office.com/en-us/business/compare-office-365-for-busine…
Neothink is a Ohio-based Microsoft Partner that already works with CLEVNET and other libraries. Their contact sheet says "Contact Neothink at 440-944-8446 or info@neothink.net to learn how your library may be eligible for free cloud-based email services provided by Microsoft." We haven't found a link to any information about such a Microsoft service.
One thing we would NOT recommend, based on our experience, is trying to build and maintain your own system, unless you have a team of email experts. Modern email systems are just too complex.
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A couple more for the list:
Here are the links to the Educational and Government plans for Exchange Online (Office 365):
http://products.office.com/en-us/academic/compare-office-365-education-plans
https://products.office.com/en-us/government/compare-office-365-government-plans
You can get Office 365 if you have been approved (by Microsoft) as an Education E3 license for staff ($4.50) and E1 for public PC (free). Here is the link: http://products.office.com/en-us/academic/compare-office-365-education-….
GoDaddy is about $150 for 3 years of email and an additional $90 for the domain. That gets (we think) 40 email addresses.