Send SMTPUTF8 if the message needs it and the server supports it.

Before this commit, Envelope would throw InvalidArgumentException when a
unicode sender address was used. Now, that error is thrown slightly later,
is thrown for recipient addresses as well, but is not thrown if the
next-hop server supports SMTPUTF8.

As a side effect, transports that use JSON APIs to ESPs can also use
unicode addresses if the ESP supports that (many do, many don't).

Author: arnt

src/Symfony/Component/Mailer/CHANGELOG.md

@@ -5,6 +5,7 @@ CHANGELOG
 ---
 
  * Make `TransportFactoryTestCase` compatible with PHPUnit 10+
+ * Support unicode email addresses such as "dømi@dømi.fo", no client changes needed
 
 7.1
 ---

src/Symfony/Component/Mailer/Envelope.php

@@ -44,10 +44,6 @@ public static function create(RawMessage $message): self
 
     public function setSender(Address $sender): void
     {
-        // to ensure deliverability of bounce emails independent of UTF-8 capabilities of SMTP servers
-        if (!preg_match('/^[^@\x80-\xFF]++@/', $sender->getAddress())) {
-            throw new InvalidArgumentException(\sprintf('Invalid sender "%s": non-ASCII characters not supported in local-part of email.', $sender->getAddress()));
-        }
         $this->sender = $sender;
     }
 
@@ -87,13 +83,28 @@ public function getRecipients(): array
     }
 
     /**
+
+      * Returns true if any address' localpart contains at least one
+      * non-ASCII character, and false if all addresses have all-ASCII
+      * localparts.
+      *
+      * This helps to decide whether to the SMTPUTF8 extensions (RFC
+      * 6530 and following) for any given message.
+      *
+      * The SMTPUTF8 extension is strictly required if any address
+      * contains a non-ASCII character in its localpart. If non-ASCII
+      * is only used in domains (e.g. horst@freiherr-von-mühlhausen.de)
+      * then it is possible to to send the message using IDN encoding
+      * instead of SMTPUTF8. The most common software will display the
+      * message as intended.
+      *
       * @return bool
       */
     public function anyAddressHasUnicodeLocalpart(): bool
     {
-        if($this->sender->hasUnicodeLocalpart())
+        if($this->getSender()->hasUnicodeLocalpart())
             return true;
-        foreach($this->recipients as $r)
+        foreach($this->getRecipients() as $r)
             if($r->hasUnicodeLocalpart())
                 return true;
         return false;

src/Symfony/Component/Mailer/Tests/EnvelopeTest.php

@@ -29,13 +29,6 @@ public function testConstructorWithAddressSender()
         $this->assertEquals(new Address('[email protected]'), $e->getSender());
     }
 
-    public function testConstructorWithAddressSenderAndNonAsciiCharactersInLocalPartOfAddress()
-    {
-        $this->expectException(InvalidArgumentException::class);
-        $this->expectExceptionMessage('Invalid sender "fabiè[email protected]": non-ASCII characters not supported in local-part of email.');
-        new Envelope(new Address('fabiè[email protected]'), [new Address('[email protected]')]);
-    }
-
     public function testConstructorWithNamedAddressSender()
     {
         $e = new Envelope($sender = new Address('[email protected]', 'Fabien'), [new Address('[email protected]')]);
@@ -81,14 +74,6 @@ public function testSenderFromHeaders()
         $this->assertEquals($from, $e->getSender());
     }
 
-    public function testSenderFromHeadersFailsWithNonAsciiCharactersInLocalPart()
-    {
-        $this->expectException(InvalidArgumentException::class);
-        $this->expectExceptionMessage('Invalid sender "fabiè[email protected]": non-ASCII characters not supported in local-part of email.');
-        $message = new Message(new Headers(new PathHeader('Return-Path', new Address('fabiè[email protected]'))));
-        Envelope::create($message)->getSender();
-    }
-
     public function testSenderFromHeadersWithoutFrom()
     {
         $headers = new Headers();

src/Symfony/Component/Mailer/Tests/Transport/Smtp/EsmtpTransportTest.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\Mailer\Tests\Transport\Smtp;
 
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Exception\InvalidArgumentException;
 use Symfony\Component\Mailer\Exception\TransportException;
 use Symfony\Component\Mailer\Transport\Smtp\Auth\CramMd5Authenticator;
 use Symfony\Component\Mailer\Transport\Smtp\Auth\LoginAuthenticator;
@@ -62,6 +63,37 @@ public function testExtensibility()
         $this->assertContains("RCPT TO:<[email protected]> NOTIFY=FAILURE\r\n", $stream->getCommands());
     }
 
+    public function testSmtputf8()
+    {
+        $stream = new DummyStream();
+        $transport = new Smtputf8EsmtpTransport(stream: $stream);
+
+        $message = new Email();
+        $message->from('info@dømi.fo');
+        $message->addTo('dømi@dømi.fo');
+        $message->text('.');
+
+        $transport->send($message);
+
+        $this->assertContains("MAIL FROM:<[email protected]> SMTPUTF8\r\n", $stream->getCommands());
+        $this->assertContains("RCPT TO:<dø[email protected]>\r\n", $stream->getCommands());
+    }
+
+    public function testMissingSmtputf8()
+    {
+        $stream = new DummyStream();
+        $transport = new EsmtpTransport(stream: $stream);
+
+        $message = new Email();
+        $message->from('info@dømi.fo');
+        $message->addTo('dømi@dømi.fo');
+        $message->text('.');
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Invalid addresses: non-ASCII characters not supported in local-part of email.');
+        $transport->send($message);
+    }
+
     public function testConstructorWithDefaultAuthenticators()
     {
         $stream = new DummyStream();
@@ -270,3 +302,17 @@ public function executeCommand(string $command, array $codes): string
         return $response;
     }
 }
+
+class Smtputf8EsmtpTransport extends EsmtpTransport
+{
+    public function executeCommand(string $command, array $codes): string
+    {
+        $response = parent::executeCommand($command, $codes);
+
+        if (str_starts_with($command, 'EHLO ')) {
+            $response .= "250 SMTPUTF8\r\n";
+        }
+
+        return $response;
+    }
+}

src/Symfony/Component/Mailer/Transport/Smtp/EsmtpTransport.php

@@ -195,6 +195,11 @@ private function parseCapabilities(string $ehloResponse): array
         return $capabilities;
     }
 
+    protected function serverSupportsSmtputf8(): bool
+    {
+        return \array_key_exists('SMTPUTF8', $this->capabilities);
+    }
+
     private function handleAuth(array $modes): void
     {
         if (!$this->username) {

src/Symfony/Component/Mailer/Transport/Smtp/SmtpTransport.php

@@ -14,6 +14,7 @@
 use Psr\EventDispatcher\EventDispatcherInterface;
 use Psr\Log\LoggerInterface;
 use Symfony\Component\Mailer\Envelope;
+use Symfony\Component\Mailer\Exception\InvalidArgumentException;
 use Symfony\Component\Mailer\Exception\LogicException;
 use Symfony\Component\Mailer\Exception\TransportException;
 use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
@@ -211,7 +212,7 @@ protected function doSend(SentMessage $message): void
 
         try {
             $envelope = $message->getEnvelope();
-            $this->doMailFromCommand($envelope->getSender()->getEncodedAddress());
+            $this->doMailFromCommand($envelope->getSender()->getEncodedAddress(), $envelope->anyAddressHasUnicodeLocalpart());
             foreach ($envelope->getRecipients() as $recipient) {
                 $this->doRcptToCommand($recipient->getEncodedAddress());
             }
@@ -244,14 +245,22 @@ protected function doSend(SentMessage $message): void
         }
     }
 
+    protected function serverSupportsSmtputf8(): bool
+    {
+        return false;
+    }
+
     private function doHeloCommand(): void
     {
         $this->executeCommand(\sprintf("HELO %s\r\n", $this->domain), [250]);
     }
 
-    private function doMailFromCommand(string $address): void
+    private function doMailFromCommand(string $address, bool $smtputf8): void
     {
-        $this->executeCommand(\sprintf("MAIL FROM:<%s>\r\n", $address), [250]);
+        if($smtputf8 && !$this->serverSupportsSmtputf8()) {
+            throw new InvalidArgumentException('Invalid addresses: non-ASCII characters not supported in local-part of email.');
+        }
+        $this->executeCommand(sprintf("MAIL FROM:<%s>%s\r\n", $address, ($smtputf8 ? " SMTPUTF8" : "")), [250]);
     }
 
     private function doRcptToCommand(string $address): void