How to disable "verify_peer" with Symfony Mailer component?

I'm configuring a mail server (postfix), with a self signed certificate, and it seems this self signed certificate is a problem for the Symfony Mailer component.

On Swiftmailer, using some configuration such as:

transport:
    stream_options:
        ssl:
            allow_self_signed: true

or

stream_options:
    ssl:
        verify_peer: false
        verify_peer_name: false

might fix it, but I can't find a way to do that on mailer (I want to use the YAML configuration files if possible).