From d4df9a2965eabbbb050a8be1a88c454c67087577 Mon Sep 17 00:00:00 2001
From: Alexis Mousset <contact@amousset.me>
Date: Sat, 27 Feb 2021 17:23:48 +0100
Subject: [PATCH] feat(transport): Add SMTPUTF8 handling (#540)

---
 src/address/envelope.rs                       |  8 ++++++
 src/address/types.rs                          |  5 ++++
 src/transport/smtp/client/async_connection.rs | 25 ++++++++++++++++++-
 src/transport/smtp/client/connection.rs       | 25 ++++++++++++++++++-
 4 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/src/address/envelope.rs b/src/address/envelope.rs
index 84c5ba1..27ed35c 100644
--- a/src/address/envelope.rs
+++ b/src/address/envelope.rs
@@ -103,6 +103,14 @@ impl Envelope {
     pub fn from(&self) -> Option<&Address> {
         self.reverse_path.as_ref()
     }
+
+    /// Check if any of the addresses in the envelope contains non-ascii chars
+    pub(crate) fn has_non_ascii_addresses(&self) -> bool {
+        self.reverse_path
+            .iter()
+            .chain(self.forward_path.iter())
+            .any(|a| !a.is_ascii())
+    }
 }
 
 #[cfg(feature = "builder")]
diff --git a/src/address/types.rs b/src/address/types.rs
index 481ea2d..99e3e2e 100644
--- a/src/address/types.rs
+++ b/src/address/types.rs
@@ -173,6 +173,11 @@ impl Address {
 
         Err(AddressError::InvalidDomain)
     }
+
+    /// Check if the address contains non-ascii chars
+    pub(super) fn is_ascii(&self) -> bool {
+        self.serialized.is_ascii()
+    }
 }
 
 impl Display for Address {
diff --git a/src/transport/smtp/client/async_connection.rs b/src/transport/smtp/client/async_connection.rs
index 7b8678b..b4bf04c 100644
--- a/src/transport/smtp/client/async_connection.rs
+++ b/src/transport/smtp/client/async_connection.rs
@@ -112,9 +112,32 @@ impl AsyncSmtpConnection {
         // Mail
         let mut mail_options = vec![];
 
-        if self.server_info().supports_feature(Extension::EightBitMime) {
+        // Internationalization handling
+        //
+        // * 8BITMIME: https://tools.ietf.org/html/rfc6152
+        // * SMTPUTF8: https://tools.ietf.org/html/rfc653
+
+        // Check for non-ascii addresses and use the SMTPUTF8 option if any.
+        if envelope.has_non_ascii_addresses() {
+            if !self.server_info().supports_feature(Extension::SmtpUtfEight) {
+                // don't try to send non-ascii addresses (per RFC)
+                return Err(Error::Client(
+                    "Envelope contains non-ascii chars but server does not support SMTPUTF8",
+                ));
+            }
+            mail_options.push(MailParameter::SmtpUtfEight);
+        }
+
+        // Check for non-ascii content in message
+        if !email.is_ascii() {
+            if !self.server_info().supports_feature(Extension::EightBitMime) {
+                return Err(Error::Client(
+                    "Message contains non-ascii chars but server does not support 8BITMIME",
+                ));
+            }
             mail_options.push(MailParameter::Body(MailBodyParameter::EightBitMime));
         }
+
         try_smtp!(
             self.command(Mail::new(envelope.from().cloned(), mail_options))
                 .await,
diff --git a/src/transport/smtp/client/connection.rs b/src/transport/smtp/client/connection.rs
index b19ef2b..362fa99 100644
--- a/src/transport/smtp/client/connection.rs
+++ b/src/transport/smtp/client/connection.rs
@@ -82,9 +82,32 @@ impl SmtpConnection {
         // Mail
         let mut mail_options = vec![];
 
-        if self.server_info().supports_feature(Extension::EightBitMime) {
+        // Internationalization handling
+        //
+        // * 8BITMIME: https://tools.ietf.org/html/rfc6152
+        // * SMTPUTF8: https://tools.ietf.org/html/rfc653
+
+        // Check for non-ascii addresses and use the SMTPUTF8 option if any.
+        if envelope.has_non_ascii_addresses() {
+            if !self.server_info().supports_feature(Extension::SmtpUtfEight) {
+                // don't try to send non-ascii addresses (per RFC)
+                return Err(Error::Client(
+                    "Envelope contains non-ascii chars but server does not support SMTPUTF8",
+                ));
+            }
+            mail_options.push(MailParameter::SmtpUtfEight);
+        }
+
+        // Check for non-ascii content in message
+        if !email.is_ascii() {
+            if !self.server_info().supports_feature(Extension::EightBitMime) {
+                return Err(Error::Client(
+                    "Message contains non-ascii chars but server does not support 8BITMIME",
+                ));
+            }
             mail_options.push(MailParameter::Body(MailBodyParameter::EightBitMime));
         }
+
         try_smtp!(
             self.command(Mail::new(envelope.from().cloned(), mail_options)),
             self