Do not set minimal TLS version for SMTP manually

src/smtp.rs

@@ -85,7 +85,6 @@ impl Smtp {
                 .danger_accept_invalid_hostnames(true)
                 .danger_accept_invalid_certs(true),
         }
-        .min_protocol_version(Some(DEFAULT_TLS_PROTOCOLS[0]))
         .build()
         .unwrap();