fix: return HTTP 200 because madmail expects it, and make sure https is immediately retried when SMTP fails (#153)

filtermail/src/http_server.rs

@@ -137,7 +137,7 @@ impl<H: SmtpHandler + 'static> Service<Request<Incoming>> for MxDelivService<H>
 
             match handler.handle_data(&mut envelope).await {
                 Ok(response) => Ok(Response::builder()
-                    .status(201)
+                    .status(200)
                     .body(Full::new(Bytes::from(response)).boxed())?),
                 Err(e) => Ok(Response::builder()
                     .status(400)

filtermail/src/transport.rs

@@ -247,16 +247,14 @@ impl TransportHandler {
                         // We only want to try other MX hosts if we encounter a problem
                         // related to connection.
                         // (So we don't spam other servers if the message is actually rejected.)
-                        crate::error::Error::Io(io_err) => {
+                        crate::error::Error::Io(_)
-                            log::warn!("I/O error relaying to mail server {mx_host}: {io_err}");
+                        | crate::error::Error::ConnectionFailed(_)
-                            continue 'try_relay;
+                        | crate::error::Error::Tls(_) => {
-                        }
+                            // Make sure we quickly retry HTTP if SMTP failed to connect
-                        crate::error::Error::ConnectionFailed(_) => {
+                            mxdeliv_unsupported_hosts.remove(&mx_host).await;
-                            log::warn!("Failed to connect to mail server {mx_host}: {error}");
+                            log::warn!(
-                            continue 'try_relay;
+                                "Connection error relaying to mail server {mx_host}: {error}"
-                        }
+                            );
-                        crate::error::Error::Tls(tls_err) => {
-                            log::warn!("TLS error relaying to mail server {mx_host}: {tls_err}");
                             continue 'try_relay;
                         }
                         _ => {