The key to figuring this out is determining what e-mail server software they are using, and is it behind an office firewall. If it is behind an office firewall, they need to provide you with a virtual private network connection, often either Citrix or Frac based VPN. Citrix often requires Java, which has been problematic on Macs since the discovery of the Flashback malware, which I reference the latest updates here:
https://discussions.apple.com/docs/DOC-3261
If it is Exchange without a firewall, sometimes they setup a web based Exchange service you can connect to. That might require running a different web browser if the built-in Exchange support on Mac OS X Mail or Microsoft Outlook 2011 for Mac doesn't work*:
http://www.macmaps.com/browser.html
Or running Windows on your Mac:
https://discussions.apple.com/docs/DOC-2741
If they are using Lotus Notes, there is a Lotus Notes client for the Mac:
http://www-01.ibm.com/support/docview.wss?uid=swg21160099
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