If you are running IIS7 and Windows 2008, you may need to increase WCF settings:

1. Open Windows Explorer.
2. Navigate to C:\Program Files\Microsoft\Exchange Server\ClientAccess\exchweb\ews
3. Open the file Web.Config in a text editor like Notepad.
4. Find all XML tags starting with maxReceivedMessageSize=
5. Change existing values to maxReceivedMessageSize="104857600"
6. Save the file.
7. Open a Command Prompt (cmd.exe).
8. Type: cd %windir%\system32\inetsrv
9. Type: appcmd.exe set config "Default Web Site/ews" -section:requestFiltering -requestLimits.maxAllowedContentLength:104857600
10. Run: iisreset