Connecting Discourse to postalserver.io for SMTP

Installation
1

Hey, I’m trying to connect my Discourse to a self hosted postalserver.io SMTP server. I get the following error from discourse

Jobs::HandledExceptionWrapper: Wrapped OpenSSL::SSL::SSLError: SSL_connect SYSCALL returned=5 errno=0 peeraddr=x.x.x.x:25 state=SSLv3/TLS write client hello

2 
DISCOURSE_SMTP_ADDRESS: <address>
DISCOURSE_SMTP_PORT: 25
DISCOURSE_SMTP_USER_NAME: <username>
DISCOURSE_SMTP_PASSWORD: "<password>"
DISCOURSE_SMTP_ENABLE_START_TLS: true           # (optional, default true)
DISCOURSE_SMTP_DOMAIN: <domain>
DISCOURSE_NOTIFICATION_EMAIL: <no-reply>
DISCOURSE_SMTP_AUTHENTICATION: "plain"
DISCOURSE_SMTP_OPENSSL_VERIFY_MODE: none