Postfix with Swiftmailer SSL Connect error

I've already made a thread, but it's awaiting moderation for a while now. I read somewhere it may be because of posted links, so I'm trying this again.

Your operating system ‪Ubuntu 14.04.4 LTS‬
Your current used Plesk- Product 12.5.30 Update #44 ,
Your depending installed mail - server software postfix

I have a mailserver with Postfix, I'm trying to send mail using the Symfony framework, which uses Swiftmailer to send mail. I've tried sending/receiving mail with...

Postfix with Swiftmailer SSL Connect error