No sé qué pasa con el servicio SMTP

[satonotdead]

Necesitas revisar la opción de seguridad porque no es muy precisa y necesitas desactivarla (sin comprometer tu seguridad).

Setting up SMTP

If you want to disable TLS, you need to uncomment this line, and set it to false: #DISCOURSE_SMTP_ENABLE_START_TLS: true # (optional, default true) However, there’s no relationship between POODLE and newer TLS protocol versions, nor is there any relationship between SMTP and POP3. Mailgun does support TLS on SMTP connections, they just don’t support it correctly.