Content-Type Header and Axis2

I see some issues when set the "Content-Type" Header  in synapse. Aixs2 doesn't obey the "Content-Type" header, when the message conatins  different messageType.

Before sending a soap message to an endpoint in synapse, if we set the "Content-Type" as text/plain, axis2 sends out  the message with text/xml content-type. But if we set messageType property as text/plain, then content-type header of the outgoing message is set to "text/plain".  This is bit confusing as in the documentation, i find that, "messageType" property is used to select correct MessageFormatter.
There are three properties ,that are related to message-type,content-type which can be set in aixs2/transport scopes.

As in the documentations,
<property name="messageType" value="text/plain" scope="axis2" type="STRING"/>
can be used to select right Messageformatter.

<property name="ContentType" value="text/plain" scope="axis2" type="STRING"/>
can be used to select right MessageBuilders

To set the Content-Type transport header,we can use following property.

 <property name="Content-Type" value="text/plain" scope="transport" type="STRING"/>

But the issue is,

When i do following setting in synapse, aixs2 sends out the message with text/xml content-type.

<inSequence>
      <property name="Content-Type" value="text/plain" scope="transport" type="STRING"/>
         <send>
            <endpoint>
                   <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
            </endpoint>
       </send>

After setting the "messageType" property only i see the correct content-type is set.