Reinstate the restriction that the sender's localpart must be all-ASCII.

This commit also adds a test that Symfony chooses IDN encoding when
possible (to be compatible with all email receivers), and adjusts a couple
of tests to match the name used in the main source code.

Author: arnt

Envelope.php

@@ -44,6 +44,10 @@ 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;
     }
 

Tests/EnvelopeTest.php

@@ -13,9 +13,11 @@
 
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Mailer\Envelope;
+use Symfony\Component\Mailer\Exception\InvalidArgumentException;
 use Symfony\Component\Mailer\Exception\LogicException;
 use Symfony\Component\Mime\Address;
 use Symfony\Component\Mime\Header\Headers;
+use Symfony\Component\Mime\Header\PathHeader;
 use Symfony\Component\Mime\Message;
 use Symfony\Component\Mime\RawMessage;
 
@@ -27,6 +29,13 @@ 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]')]);
@@ -72,6 +81,14 @@ 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();

Tests/Transport/Smtp/EsmtpTransportTest.php

@@ -63,10 +63,10 @@ public function testExtensibility()
         $this->assertContains("RCPT TO:<[email protected]> NOTIFY=FAILURE\r\n", $stream->getCommands());
     }
 
-    public function testSmtputf8()
+    public function testSmtpUtf8()
     {
         $stream = new DummyStream();
-        $transport = new Smtputf8EsmtpTransport(stream: $stream);
+        $transport = new SmtpUtf8EsmtpTransport(stream: $stream);
 
         $message = new Email();
         $message->from('info@dømi.fo');
@@ -79,7 +79,7 @@ public function testSmtputf8()
         $this->assertContains("RCPT TO:<dø[email protected]>\r\n", $stream->getCommands());
     }
 
-    public function testMissingSmtputf8()
+    public function testMissingSmtpUtf8()
     {
         $stream = new DummyStream();
         $transport = new EsmtpTransport(stream: $stream);
@@ -94,6 +94,22 @@ public function testMissingSmtputf8()
         $transport->send($message);
     }
 
+    public function testSmtpUtf8FallbackToIDN()
+    {
+        $stream = new DummyStream();
+        $transport = new EsmtpTransport(stream: $stream);
+
+        $message = new Email();
+        $message->from('info@dømi.fo'); // UTF8 only in the domain
+        $message->addTo('[email protected]');
+        $message->text('.');
+
+        $transport->send($message);
+
+        $this->assertContains("MAIL FROM:<[email protected]>\r\n", $stream->getCommands());
+        $this->assertContains("RCPT TO:<[email protected]>\r\n", $stream->getCommands());
+    }
+
     public function testConstructorWithDefaultAuthenticators()
     {
         $stream = new DummyStream();
@@ -303,7 +319,7 @@ public function executeCommand(string $command, array $codes): string
     }
 }
 
-class Smtputf8EsmtpTransport extends EsmtpTransport
+class SmtpUtf8EsmtpTransport extends EsmtpTransport
 {
     public function executeCommand(string $command, array $codes): string
     {