This is a C# code example of a Outlook 2010 Add-in Place Button in Message Tab.
<?xml version="1.0" encoding="UTF-8"?><customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui" onLoad="Ribbon_Load">
<ribbon>
<tabs>
<tab idMso="TabNewMailMessage">
<group id="MyGroup" label="Chad Syteline">
<button id="btnExportNew" imageMso="AutoArchiveSettings" label="Send" size="large" onAction="SL_Export" />
</group>
</tab>
<tab idMso="TabReadMessage">
<group id="MyGroup2" label="Chad Syteline">
<button id="btnExportRead" imageMso="AutoArchiveSettings" label="Export" size="large" onAction="SL_Export" />
</group>
</tab>
</tabs>
</ribbon>
</customUI>