Aceptance Condition in Mail Send

Hello, i have a issue, if you have a conditional checkbox like this:

[acceptance your-consent] 
I agree to subscribe to the newsletter</a>.

And you want a conditional mail to be received just like this:
Message Body:

De: [your-name] [your-apellido] <[your-email]>
Teléfono: [your-telephone]
Asunto: [your-subject]

Body of Message:
[your-message]

And I want to add a conditional option when someone has subscribed to the newsletter, such as "You have accepted to subscribe to the newsletter"

Any idea how to do it?