If you work for a smaller company and want to get Outlook on your mobile, tell you IT guys to follow this guide!
I have excerpted the cheap and easy way here, for posterity. But go look at the original post, it has pictures.
Method #3 (easy and cheap)
Create a secondary virtual directory for Exchange that does not require SSL, and then add a registry value to point to the new virtual directory. You must use Internet Information Services (IIS) Manager to create this virtual directory for Exchange ActiveSync and Outlook Mobile Access to work. If you are using Windows Server 2003, follow these instructions:
Note: These steps affect both Outlook Mobile Access connections and Exchange ActiveSync connections. After you follow these steps, both Outlook Mobile Access and Exchange ActiveSync connections use the new virtual directory that you create.
Start Internet Information Services (IIS) Manager.
Locate the Exchange virtual directory. The default location is the following:
Web Sites\Default Web Site\Exchange
Right-click the Exchange virtual directory, click All Tasks, and then click Save Configuration to a File.
Important note: You must first disable Forms Based Authentication from the ESM BEFORE you export the virtual directory. Also, you must disable SSL on the virtual directory BEFORE you export it. After exporting you can return to FBA and SSL.
In the File name box, type a name. For example, type ExchangeVDir. Click OK.
Right-click the root of this Web site. Typically, this is Default Web Site. Click New, and then click Virtual Directory (from file).
In the Import Configuration dialog box, click Browse, locate the file that you created in step 4, click Open, and then click Read File.
Under Select a configuration to import , click Exchange, and then click OK. A dialog box will appear that states that the “virtual directory already exists.”
In the Alias box, type a name for the new virtual directory that you want Exchange ActiveSync and Outlook Mobile Access to use. For example, type ExchDAV. Click OK.
Right-click the new virtual directory. In this example, click ExchDAV. Click Properties.
Click the Directory Security tab.
Under Authentication and access control, click Edit.
Make sure that only the following authentication methods are enabled, and then click OK:
Integrated Windows authentication
Under IP address and domain name restrictions, click Edit.
Click Denied access, click Add, click Single computer, type the IP address of the server that you are configuring, and then click OK.
Under Secure communications, click Edit. Make sure that Require secure channel (SSL) is not enabled, and then click OK.
Click OK, and then close the IIS Manager.
Click Start, click Run, type REGEDIT, and then click OK.
Locate the following registry subkey:
Right-click Parameters, click to New, and then click String Value.
Type ExchangeVDir, and then press ENTER. Right-click ExchangeVDir, and then click Modify.
In the Value data box, type the name of the new virtual directory that you created in step 8 preceded by a forward slash (/). For example, type /ExchDAV. Click OK.
Quit Registry Editor.
Restart the IIS Admin service. To do this, follow these steps:
Click Start, click Run, type services.msc, and then click OK.
In the list of services, right-click IIS Admin service, and then click Restart.