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
You can use:
MAILER_DSN="smtp://user:pass@localhost?encryption=ssl&stream_options[ssl][verify_peer]=false&stream_options[ssl][verify_peer_name]=false&stream_options[ssl][allow_self_signed]=true"