The :tls setting is for STARTTLS. If you’re not using starttls you should disable it. You can find a bit more context about that here: SSL connection options · Issue #298 · gen-smtp/gen_smtp · GitHub
The :tls setting is for STARTTLS. If you’re not using starttls you should disable it. You can find a bit more context about that here: SSL connection options · Issue #298 · gen-smtp/gen_smtp · GitHub