[SOLVED] Extending symfonymail components

Hi, I’m trying to replace swiftmail with symfonymail in my app.
I’ve extended the yii\swiftmailer\Message class to customize the message elements and referred the ehnanced class in the messageClass configuratin property.
Now I would do the same with the yii\symfonymailer\Message class, but it seems impossible: the reference for this class is not available for the use command.
Can someone help me? Thanks

My mistake in namespace definition.