Configuring UploadReadAheadSize for Certificate Based Authentication for ActiveSync

Scenario: When configuring Certificate Based Authentication, you will have to configure the UploadReadAheadSize property in IIS to  allow message content greater than 48K.  Without the UploadReadAheadSize properly set, some symptoms you may experience are HTTP Status codes of 413 for ActiveSync Requests in the IIS logs  and mobile devices may experience size errors when attempting to send email.

Solution:

How to set the uploadReadAheadSize in IIS 7.5

1. Launch “Internet Information Services (IIS) Manager”
2. Expand the Server field
3. Expand Sites
4. Expand Default Web Site
5. Click on Microsoft-Server-ActiveSync
6. In the Features section, double click “Configuration Editor”
7. Under “Section” select: system.webServer>serverRuntime
8. Modify the “uploadReadAheadSize” section to 36700160 for 35MB.
9. Click Apply