Yahoo is not receiving an email from swift mailer

Question

I have a system that are sending an email confirmation to the email of the user. The user use a yahoo account,He did not receive any confirmation email. I dont have any idea what is the problem.

Here is my code:

fos_user:
    db_driver: orm # other valid values are 'mongodb' and 'couchdb'
    firewall_name: main
    user_class: CC\UserBundle\Entity\User
#    change_password:
#        form:
#            type:               cc_user_change_password
#            name:               cc_user_change_password
    registration:
        confirmation:
            enabled: true
            from_email:
                address:        registration@curaconnector.com
                sender_name:    CuraConnector Registration
            template: CCUserBundle:Email:registration.html.twig
        form:
            type: CC\UserBundle\Form\Type\RegistrationType
    service:
        user_manager: pugx_user_manager
        mailer: fos_user.mailer.twig_swift
    from_email:
        address:      webmaster@curaconnector.com
        sender_name:  CuraConnector.com

I just want the email send to the yahoo account of the user. please help. thanks