Collegare Discourse a postalserver.io per SMTP

Installazione
1

Ehi, sto cercando di connettere il mio Discourse a un server SMTP self-hosted postalserver.io. Ricevo il seguente errore da 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: <indirizzo>
DISCOURSE_SMTP_PORT: 25
DISCOURSE_SMTP_USER_NAME: <nomeutente>
DISCOURSE_SMTP_PASSWORD: "<password>"
DISCOURSE_SMTP_ENABLE_START_TLS: true           # (opzionale, default true)
DISCOURSE_SMTP_DOMAIN: <dominio>
DISCOURSE_NOTIFICATION_EMAIL: <no-reply>
DISCOURSE_SMTP_AUTHENTICATION: "plain"
DISCOURSE_SMTP_OPENSSL_VERIFY_MODE: none