THE INFORMATION IN THIS ARTICLE APPLIES TO:

• Mail Express, all versions

SYMPTOM

Mail Express Outlook Add-in user logon using Windows authentication fails with a (400) Bad request error.

CAUSE

Apache Tomcat, the web server used by Mail Express, imposes a limit on the size of the header of each HTTP request. The default limit is 8192 bytes. If the header of an HTTP request exceeds this limit (such as when a user has numerous AD accounts and group memberships), Tomcat closes the TCP connection, causing the authentication to fail.

WORKAROUND

Add the maxHttpHeaderSize value to the first Connector in the <Installation Directory>\conf\server.xml file, as described below. The Mail Express Server service must be restarted for any changes to take effect.

To configure the Mail Express Server to allow a larger header size:

1. Shut down the Mail Express Server service.
2. Using a text editor such as Notepad, edit the configuration file “<Mail Express Server Installation Directory>\conf \server.xml”
3. Locate the SSL Connector definition XML Element by searching for the text "port=443". The element will be similar to:

   	<Connector 
   			address="192.168.1.58"
   			port="443"
   			protocol="HTTP/1.1"
   			connectionTimeout="20000"
   			keepAliveTimeout="20000"
   			enableLookups="true" 
   			disableUploadTimeout="true"
   			acceptCount="100"
   			maxThreads="200"
   			scheme="https"
   			secure="true"
   			SSLEnabled="true"
   			SSLProtocol="all"
   			SSLCipherSuite="ALL:!ADH:!SSLv2:!EXPORT40:!EXP:!LOW"
   			SSLCertificateFile="${catalina.home}\conf\MailExpress.crt" 
   			SSLCertificateKeyFile="${catalina.home}\conf\MailExpress.key"
   			SSLPassword="mailexpress"
   			SSLVerifyClient="none"
   			SSLVerifyDepth="10"/>
   	

4. Add the maxHttpHeaderSize attribute into the “Connector” definition. For example: maxHttpHeaderSize="16384"

The number can range from 8192 to 65536. The resulting Connector definition should resemble the following example:

	<Connector
			address="192.168.1.58"
			port="443"
			protocol="HTTP/1.1"
			connectionTimeout="20000"
			keepAliveTimeout="20000"
			enableLookups="true" 
			disableUploadTimeout="true"
			acceptCount="100"
			maxThreads="200"
			maxHttpHeaderSize="16384"
			scheme="https"
			secure="true"
			SSLEnabled="true"
			SSLProtocol="all"
			SSLCipherSuite="ALL:!ADH:!SSLv2:!EXPORT40:!EXP:!LOW"
			SSLCertificateFile="${catalina.home}\conf\MailExpress.crt" 
			SSLCertificateKeyFile="${catalina.home}\conf\MailExpress.key"
			SSLPassword="mailexpress"
			SSLVerifyClient="none"
			SSLVerifyDepth="10"/>

5. Save the changes to the file.
6. Start the Mail Express Server service.