feature #33471 [Mailer] Check email validity before opening an SMTP connection (fabpot)

This PR was merged into the 4.4 branch.

Discussion
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[Mailer] Check email validity before opening an SMTP connection

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | yes-ish
| New feature?  | yes
| BC breaks?    | no-ish
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

When using an SMTP server to send emails, the connection to the SMTP server happens before being sure that the email to sent is valid. That does not happen with HTTP transports.

This pull request implements a new method to be sure that we don't connect to the SMTP server if the email is not valid.

Commits
-------

dc376f52a5 [Mailer] Check email validity before opening an SMTP connection

Author: fabpot

SentMessage.php

@@ -29,6 +29,8 @@ class SentMessage
      */
     public function __construct(RawMessage $message, SmtpEnvelope $envelope)
     {
+        $message->ensureValidity();
+
         $this->raw = $message instanceof Message ? new RawMessage($message->toIterable()) : $message;
         $this->original = $message;
         $this->envelope = $envelope;

Transport/Smtp/SmtpTransport.php

@@ -104,18 +104,15 @@ public function getLocalDomain(): string
 
     public function send(RawMessage $message, SmtpEnvelope $envelope = null): ?SentMessage
     {
-        $this->ping();
-        if (!$this->started) {
-            $this->start();
-        }
-
         try {
             $message = parent::send($message, $envelope);
         } catch (TransportExceptionInterface $e) {
-            try {
-                $this->executeCommand("RSET\r\n", [250]);
-            } catch (TransportExceptionInterface $_) {
-                // ignore this exception as it probably means that the server error was final
+            if ($this->started) {
+                try {
+                    $this->executeCommand("RSET\r\n", [250]);
+                } catch (TransportExceptionInterface $_) {
+                    // ignore this exception as it probably means that the server error was final
+                }
             }
 
             throw $e;
@@ -163,6 +160,11 @@ public function executeCommand(string $command, array $codes): string
 
     protected function doSend(SentMessage $message): void
     {
+        $this->ping();
+        if (!$this->started) {
+            $this->start();
+        }
+
         try {
             $envelope = $message->getEnvelope();
             $this->doMailFromCommand($envelope->getSender()->getAddress());

Transport/Smtp/Stream/SocketStream.php

@@ -26,7 +26,7 @@ final class SocketStream extends AbstractStream
     private $url;
     private $host = 'localhost';
     private $port = 465;
-    private $timeout = 15;
+    private $timeout = 5;
     private $tls = true;
     private $sourceIp;
     private $streamContextOptions = [];