It is working with these parameters (PORT - 587, AUTHENTICATION - “login”):
## TODO: The SMTP mail server used to validate new accounts and send notifications
DISCOURSE_SMTP_ADDRESS: pap.serveriai.lt
DISCOURSE_SMTP_PORT: 587
DISCOURSE_SMTP_USER_NAME: robo@magved.lt
DISCOURSE_SMTP_PASSWORD: topsecret
DISCOURSE_SMTP_ENABLE_START_TLS: true # (optional, default true)
DISCOURSE_SMTP_AUTHENTICATION: "login"
DISCOURSE_SMTP_OPENSSL_VERIFY_MODE: none
Email provider gave wrong port and authentication parameters.