This makes no sense. If I connect to the internet using my own celluar "Verizon connect" usb dongle, then I can download my rackspace email just fine. But if I connect to the internet using the office network (wired or wireless - it doesn't matter), which uses Comcast, I can't download that same email.
Why would the isp make any difference as long as Outlook is configured correctly?
Plus, other users in the office are able to get their email just fine, same source, same network, same hardware and software setups.
Windows 7 (but the same was true when I tried to connect with my old XP laptop)
Email hosted by rackspace.