MTA: Do not convert e-mail local parts to lowercase (fixes #1916)

crates/smtp/src/queue/dsn.rs

@@ -39,7 +39,7 @@ impl SendDsn for Server {
             if let Some(dsn) = message.build_dsn(self).await {
                 let mut dsn_message = self.new_message("", message.span_id);
                 dsn_message
-                    .add_recipient_parts(message.message.return_path.as_str(), self)
+                    .add_recipient(message.message.return_path.as_str(), self)
                     .await;
 
                 // Sign message

crates/smtp/src/queue/mod.rs

@@ -399,6 +399,49 @@ pub fn instant_to_timestamp(now: Instant, time: Instant) -> u64 {
         + time.checked_duration_since(now).map_or(0, |d| d.as_secs())
 }
 
+impl Recipient {
+    pub fn new(address: impl AsRef<str>) -> Self {
+        Recipient {
+            address: address.to_lowercase_domain(),
+            status: Status::Scheduled,
+            flags: 0,
+            orcpt: None,
+            retry: Schedule::now(),
+            notify: Schedule::now(),
+            expires: QueueExpiry::Attempts(0),
+            queue: QueueName::default(),
+        }
+    }
+
+    pub fn with_flags(mut self, flags: u64) -> Self {
+        self.flags = flags;
+        self
+    }
+
+    pub fn with_orcpt(mut self, orcpt: Option<String>) -> Self {
+        self.orcpt = orcpt;
+        self
+    }
+
+    pub fn address(&self) -> &str {
+        &self.address
+    }
+
+    pub fn domain_part(&self) -> &str {
+        self.address.domain_part()
+    }
+}
+
+impl ArchivedRecipient {
+    pub fn address(&self) -> &str {
+        self.address.as_str()
+    }
+
+    pub fn domain_part(&self) -> &str {
+        self.address.domain_part()
+    }
+}
+
 pub trait InstantFromTimestamp {
     fn to_instant(&self) -> Instant;
 }
@@ -418,10 +461,28 @@ impl InstantFromTimestamp for u64 {
 }
 
 pub trait DomainPart {
+    fn to_lowercase_domain(&self) -> String;
     fn domain_part(&self) -> &str;
 }
 
 impl<T: AsRef<str>> DomainPart for T {
+    fn to_lowercase_domain(&self) -> String {
+        let address = self.as_ref();
+        if let Some((local, domain)) = address.rsplit_once('@') {
+            let mut address = String::with_capacity(address.len());
+            address.push_str(local);
+            address.push('@');
+            for ch in domain.chars() {
+                for ch in ch.to_lowercase() {
+                    address.push(ch);
+                }
+            }
+            address
+        } else {
+            address.to_string()
+        }
+    }
+
     #[inline(always)]
     fn domain_part(&self) -> &str {
         self.as_ref()

crates/smtp/src/queue/spool.rs

@@ -13,7 +13,7 @@ use crate::queue::{
     DomainPart, FROM_AUTHENTICATED, FROM_AUTOGENERATED, FROM_DSN, FROM_REPORT,
     FROM_UNAUTHENTICATED, FROM_UNAUTHENTICATED_DMARC, MessageWrapper,
 };
-use common::config::smtp::queue::{QueueExpiry, QueueName};
+use common::config::smtp::queue::QueueName;
 use common::ipc::QueueEvent;
 use common::{KV_LOCK_QUEUE_MESSAGE, Server};
 use std::borrow::Cow;
@@ -39,7 +39,7 @@ pub struct QueuedMessages {
 }
 
 pub trait SmtpSpool: Sync + Send {
-    fn new_message(&self, return_path: impl Into<String>, span_id: u64) -> MessageWrapper;
+    fn new_message(&self, return_path: impl AsRef<str>, span_id: u64) -> MessageWrapper;
 
     fn next_event(&self, queue: &mut Queue) -> impl Future<Output = QueuedMessages> + Send;
 
@@ -68,7 +68,7 @@ pub trait SmtpSpool: Sync + Send {
 }
 
 impl SmtpSpool for Server {
-    fn new_message(&self, return_path: impl Into<String>, span_id: u64) -> MessageWrapper {
+    fn new_message(&self, return_path: impl AsRef<str>, span_id: u64) -> MessageWrapper {
         let created = SystemTime::now()
             .duration_since(SystemTime::UNIX_EPOCH)
             .map_or(0, |d| d.as_secs());
@@ -80,7 +80,7 @@ impl SmtpSpool for Server {
             span_id,
             message: Message {
                 created,
-                return_path: return_path.into(),
+                return_path: return_path.to_lowercase_domain(),
                 recipients: Vec::with_capacity(1),
                 flags: 0,
                 env_id: None,
@@ -483,18 +483,9 @@ impl MessageWrapper {
         true
     }
 
-    pub async fn add_recipient_parts(&mut self, rcpt: impl Into<String>, server: &Server) {
+    pub async fn add_recipient(&mut self, rcpt: impl AsRef<str>, server: &Server) {
         // Resolve queue
-        self.message.recipients.push(Recipient {
-            address: rcpt.into(),
-            status: Status::Scheduled,
-            flags: 0,
-            orcpt: None,
-            retry: Schedule::now(),
-            notify: Schedule::now(),
-            expires: QueueExpiry::Attempts(0),
-            queue: QueueName::default(),
-        });
+        self.message.recipients.push(Recipient::new(rcpt));
         let queue = server.get_queue_or_default(
             &server
                 .eval_if::<String, _>(
@@ -515,11 +506,6 @@ impl MessageWrapper {
         recipient.queue = queue.virtual_queue;
     }
 
-    pub async fn add_recipient(&mut self, rcpt: impl AsRef<str>, server: &Server) {
-        let rcpt = rcpt.as_ref().to_lowercase();
-        self.add_recipient_parts(rcpt, server).await;
-    }
-
     pub async fn save_changes(mut self, server: &Server, prev_event: Option<u64>) -> bool {
         // Release quota for completed deliveries
         let mut batch = BatchBuilder::new();