Office 365 offers the best email backend for Macs
It's hard to beat Microsoft's Office 365-hosted Exchange email services. For $5.00 (USD) per user, per month (paid annually), you'll be challenged licensing, installing, administering, maintaining, and securing your own email server -- regardless of platform -- for less.
Microsoft's Office 365 Business Essentials plan, which scales to support up to 300 users, is compatible with Microsoft Office 2011 for Mac. The platform also works with recent versions of OS X's integrated Mail, Calendar, and Contacts applications.
Even older shops still running Entourage 2008 Web Services Edition should find the platform compatible, although such offices should expect to have to make Entourage configuration changes, including changing the Exchange account settings, as described on Microsoft's Office Online site. That said, I recommend moving off Entourage to OS X Mail or Outlook 2011 for Mac. Apple businesses can upgrade to Microsoft's Office 365 Business plan for only $8.25 per user, per month (again, paid annually), and that includes fully installed Office application licenses.
Microsoft indicates on its Office Online site that Apple users running Mac OS 10.6 or newer can use the integrated Mac Mail application with hosted Exchange services. OS X users stuck on 10.4 and 10.5 can still connect the integrated Mail app to Exchange services as long as the account is connected without using IMAP or POP.
In my experience, clients have been well served using OS 10.6 and iOS 6 and newer with hosted Exchange. Connecting new tablets, smartphones, and Macs to hosted Exchange services typically proves to be a simple task that requires less than five minutes, assuming the user knows the correct server name, username, and password for the account. And when Apple shops add Windows machines, it's very easy to connect Outlook to the hosted Exchange platform.
In addition to enterprise-class calendar sharing, Apple businesses implementing an Office 365 Business Essentials plan receive online conferencing capabilities, instant messaging, and Skype connectivity, plus file storage, sharing features, and mobile versions of Word, Excel, and PowerPoint. Outlook Web Access functionality is included as well.
Businesses need not worry that individual email message attachments and mailbox size restrictions will prove artificially low. Office 365 Business Essentials mailboxes can grow up to 50 GB, and attachments up to 25 MB are supported.
Does your organization use Microsoft's Office 365-hosted Exchange email services on Apple computers and devices? If so, what pros and cons have you experienced? Let us know in the discussion thread below.