My users need off-line / disconnected access to their email and I do not want to install Outlook or Thunderbird. What options do I have?
Try Zimbra desktop - it's free! The free Zimbra Desktop client allows you to meld the online and offline worlds – storing and synching your email, calendar, contacts, files and documents in the cloud, yet having them locally accessible when on the road. Zimbra Desktop aggregates information across accounts (Zimbra, Yahoo! Mail, Gmail, Hotmail, etc.) and social networks (Facebook, Digg, Twitter, etc.) to help make communicating & sharing information easier than ever.