feat: improve logging of connection failures

Previously it was not always clear whether IMAP or SMTP connection
failed and what was the endpoint used.

src/imap.rs

@@ -356,10 +356,10 @@ impl Imap {
                 context,
                 self.proxy_config.clone(),
                 self.strict_tls,
-                connection_candidate,
+                &connection_candidate,
             )
             .await
-            .context("IMAP failed to connect")
+            .with_context(|| format!("IMAP failed to connect to {connection_candidate}"))
             {
                 Ok(client) => client,
                 Err(err) => {

src/imap/client.rs

@@ -150,7 +150,7 @@ impl Client {
             Err(err) => {
                 warn!(
                     context,
-                    "Failed to connect to {host} ({resolved_addr}): {err:#}."
+                    "IMAP failed to connect to {host} ({resolved_addr}): {err:#}."
                 );
                 Err(err)
             }
@@ -161,7 +161,7 @@ impl Client {
         context: &Context,
         proxy_config: Option<ProxyConfig>,
         strict_tls: bool,
-        candidate: ConnectionCandidate,
+        candidate: &ConnectionCandidate,
     ) -> Result<Self> {
         let host = &candidate.host;
         let port = candidate.port;

src/net.rs

@@ -109,8 +109,8 @@ pub(crate) async fn connect_tcp_inner(
 ) -> Result<Pin<Box<TimeoutStream<TcpStream>>>> {
     let tcp_stream = timeout(TIMEOUT, TcpStream::connect(addr))
         .await
-        .context("connection timeout")?
+        .context("Connection timeout")?
-        .context("connection failure")?;
+        .context("Connection failure")?;
 
     // Disable Nagle's algorithm.
     tcp_stream.set_nodelay(true)?;

src/smtp/connect.rs

@@ -136,7 +136,7 @@ async fn connection_attempt(
         Err(err) => {
             warn!(
                 context,
-                "Failed to connect to {host} ({resolved_addr}): {err:#}."
+                "SMTP failed to connect to {host} ({resolved_addr}): {err:#}."
             );
             Err(err)
         }