Application filetype association icon in Mail.app

I'm writing an OS X application that open files. I've registered for my filetype by using the info.plist as follows:

<key>CFBundleDocumentTypes</key>
<array>
    <dict>
        <key>CFBundleTypeName</key>
        <string>My File Type</string>
        <key>LSHandlerRank</key>
        <string>Owner</string>
        <key>CFBundleTypeExtensions</key>
        <array>
            <string>trip</string>
        </array>
        <key>CFBundleTypeRole</key>
        <string>Viewer</string>
        <key>CFBundleTypeIconFile</key>
        <string>filetype.icns</string>
    </dict>
</array>

In finder I see my icons for my associated filetype and double clicking the file invokes my app perfect.

When I receive a .trip file in Mail.app the icon of the attachment is just the generic one. Double clicking the file does open my application correctly. My icns file contains all the sizes, and was created with Icon Composer.

Is there a way to specify the Mail.app icon? like zip do? have I missed something? o开发者_运维知识库r is there a different way of specifying that icon.

Thanks