From 7395f76bbad293e0c666a3da8caf8f8371b86ccb Mon Sep 17 00:00:00 2001
From: mdecimus <mauro@stalw.art>
Date: Sat, 23 Aug 2025 20:31:57 +0200
Subject: [PATCH] SMTP: Do no send EHLO twice when STARTTLS is unavailable
 (fixes #2050)

---
 crates/smtp/src/outbound/delivery.rs |  4 ++-
 crates/smtp/src/outbound/session.rs  | 51 +++++++++++++++-------------
 2 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/crates/smtp/src/outbound/delivery.rs b/crates/smtp/src/outbound/delivery.rs
index b21f50ef..5a2a02a3 100644
--- a/crates/smtp/src/outbound/delivery.rs
+++ b/crates/smtp/src/outbound/delivery.rs
@@ -926,7 +926,7 @@ impl QueuedMessage {
                         .and_then(|ip| ip.host.as_deref())
                         .or(conn_strategy.ehlo_hostname.as_deref())
                         .unwrap_or(server.core.network.server_name.as_str());
-                    let params = SessionParams {
+                    let mut params = SessionParams {
                         session_id: message.span_id,
                         server: &server,
                         credentials: remote_host.credentials(),
@@ -934,6 +934,7 @@ impl QueuedMessage {
                         hostname: envelope.mx,
                         local_hostname,
                         conn_strategy,
+                        capabilities: None,
                     };
 
                     // Prepare TLS connector
@@ -1132,6 +1133,7 @@ impl QueuedMessage {
                                         continue 'next_host;
                                     } else {
                                         // TLS is not required, proceed in plain-text
+                                        params.capabilities = Some(capabilities);
                                         message
                                             .deliver(
                                                 smtp_client,
diff --git a/crates/smtp/src/outbound/session.rs b/crates/smtp/src/outbound/session.rs
index 54f6343e..b47589e7 100644
--- a/crates/smtp/src/outbound/session.rs
+++ b/crates/smtp/src/outbound/session.rs
@@ -25,6 +25,7 @@ pub struct SessionParams<'x> {
     pub server: &'x Server,
     pub hostname: &'x str,
     pub credentials: Option<&'x Credentials<String>>,
+    pub capabilities: Option<EhloResponse<String>>,
     pub is_smtp: bool,
     pub local_hostname: &'x str,
     pub conn_strategy: &'x ConnectionStrategy,
@@ -37,33 +38,37 @@ impl MessageWrapper {
         mut smtp_client: SmtpClient<T>,
         rcpt_idxs: Vec<usize>,
         statuses: &mut Vec<DeliveryResult>,
-        params: SessionParams<'_>,
+        mut params: SessionParams<'_>,
     ) {
         // Obtain capabilities
         let time = Instant::now();
-        let capabilities = match smtp_client.say_helo(&params).await {
-            Ok(capabilities) => {
-                trc::event!(
-                    Delivery(DeliveryEvent::Ehlo),
-                    SpanId = params.session_id,
-                    Hostname = params.hostname.to_string(),
-                    Details = capabilities.capabilities(),
-                    Elapsed = time.elapsed(),
-                );
+        let capabilities = if let Some(capabilities) = params.capabilities.take() {
+            capabilities
+        } else {
+            match smtp_client.say_helo(&params).await {
+                Ok(capabilities) => {
+                    trc::event!(
+                        Delivery(DeliveryEvent::Ehlo),
+                        SpanId = params.session_id,
+                        Hostname = params.hostname.to_string(),
+                        Details = capabilities.capabilities(),
+                        Elapsed = time.elapsed(),
+                    );
 
-                capabilities
-            }
-            Err(status) => {
-                trc::event!(
-                    Delivery(DeliveryEvent::EhloRejected),
-                    SpanId = params.session_id,
-                    Hostname = params.hostname.to_string(),
-                    CausedBy = from_error_status(&status),
-                    Elapsed = time.elapsed(),
-                );
-                smtp_client.quit().await;
-                statuses.push(DeliveryResult::domain(status, rcpt_idxs));
-                return;
+                    capabilities
+                }
+                Err(status) => {
+                    trc::event!(
+                        Delivery(DeliveryEvent::EhloRejected),
+                        SpanId = params.session_id,
+                        Hostname = params.hostname.to_string(),
+                        CausedBy = from_error_status(&status),
+                        Elapsed = time.elapsed(),
+                    );
+                    smtp_client.quit().await;
+                    statuses.push(DeliveryResult::domain(status, rcpt_idxs));
+                    return;
+                }
             }
         };