diff --git a/sources/Application/TwigBase/Twig/Extension.php b/sources/Application/TwigBase/Twig/Extension.php
index 2c5ebeffae..18721f9af1 100644
--- a/sources/Application/TwigBase/Twig/Extension.php
+++ b/sources/Application/TwigBase/Twig/Extension.php
@@ -153,8 +153,12 @@ class Extension
 			return twig_array_filter($oTwigEnv, $array, $arrow);
 		}, ['needs_environment' => true]);
 
-		// @since 3.3.0 N°8579
-		// Filter to remove spaces between HTML tags, overwrite the deprecated core "spaceless" filter
+		/**
+		 * Filter to remove spaces between HTML tags, overwrite the deprecated core "spaceless" filter
+		 * Usage in twig: {% apply spaceless %}some html{% endapply %}
+		 *
+		 * @since 3.2.3 3.3.0 N°8579
+		 */
 		$aFilters[] = new TwigFilter('spaceless', function (?string $content) {
 			return trim(preg_replace('/>\s+</', '><', $content ?? ''));
 		}, ['is_safe' => ['html']]);
diff --git a/sources/Core/Email/EmailSymfony.php b/sources/Core/Email/EmailSymfony.php
index 1d29aec200..fbb0120343 100644
--- a/sources/Core/Email/EmailSymfony.php
+++ b/sources/Core/Email/EmailSymfony.php
@@ -29,6 +29,7 @@ use Symfony\Component\CssSelector\Exception\ParseException;
 use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
 use Symfony\Component\Mailer\Transport;
 use Symfony\Component\Mailer\Mailer;
+use Symfony\Component\Mailer\Transport\Smtp\EsmtpTransport;
 use Symfony\Component\Mime\Email as SymfonyEmail;
 use Symfony\Component\Mime\HtmlToTextConverter\DefaultHtmlToTextConverter;
 use Symfony\Component\Mime\Part\DataPart;
@@ -184,18 +185,7 @@ class EMailSymfony extends Email
 					$sDsn = sprintf('smtp://%s%s@%s%s', $sDsnUser, $sDsnPassword, $sDsnPort, $sEncQuery);
 				}
 
-				$oTransport = Transport::fromDsn($sDsn);
-
-				// Handle peer verification
-				$oStream = $oTransport->getStream();
-				$aOptions = $oStream->getStreamOptions();
-				if (!$bVerifyPeer && array_key_exists('ssl', $aOptions)) {
-					// Disable verification
-					$aOptions['ssl']['verify_peer'] = false;
-					$aOptions['ssl']['verify_peer_name'] = false;
-					$aOptions['ssl']['allow_self_signed'] = true;
-				}
-				$oStream->setStreamOptions($aOptions);
+				$oTransport = $this->CreateSmtpTransport($sDsn, $bVerifyPeer);
 
 				$oMailer = new Mailer($oTransport);
 				break;
@@ -261,6 +251,36 @@ class EMailSymfony extends Email
 		}
 	}
 
+	/**
+	 * Build and configure an SMTP transport from a DSN string.
+	 *
+	 * Extracted from {@see SendSynchronous} to make SSL option handling independently testable.
+	 * When $bVerifyPeer is false, the ssl stream context options must be written unconditionally:
+	 * with STARTTLS the connection starts unencrypted, so the 'ssl' key is absent from the stream
+	 * options at construction time and only used later when stream_socket_enable_crypto() is called.
+	 *
+	 * @param string $sDsn       Full Symfony Mailer DSN (smtp:// or smtps://)
+	 * @param bool   $bVerifyPeer Whether to verify the peer SSL certificate
+	 *
+	 * @return \Symfony\Component\Mailer\Transport\Smtp\EsmtpTransport
+	 */
+	protected function CreateSmtpTransport(string $sDsn, bool $bVerifyPeer): EsmtpTransport
+	{
+		/** @var EsmtpTransport $oTransport */
+		$oTransport = Transport::fromDsn($sDsn);
+
+		$oStream = $oTransport->getStream();
+		$aOptions = $oStream->getStreamOptions();
+		if (!$bVerifyPeer) {
+			$aOptions['ssl']['verify_peer'] = false;
+			$aOptions['ssl']['verify_peer_name'] = false;
+			$aOptions['ssl']['allow_self_signed'] = true;
+		}
+		$oStream->setStreamOptions($aOptions);
+
+		return $oTransport;
+	}
+
 	/**
 	 * Reprocess the body of the message (if it is an HTML message)
 	 * to replace the URL of images based on attachments by a link
diff --git a/tests/php-unit-tests/unitary-tests/sources/core/Email/EmailSymfonyTest.php b/tests/php-unit-tests/unitary-tests/sources/core/Email/EmailSymfonyTest.php
index 1a289798d5..2cefa18742 100644
--- a/tests/php-unit-tests/unitary-tests/sources/core/Email/EmailSymfonyTest.php
+++ b/tests/php-unit-tests/unitary-tests/sources/core/Email/EmailSymfonyTest.php
@@ -2,6 +2,7 @@
 
 use Combodo\iTop\Core\Email\EMailSymfony;
 use Combodo\iTop\Test\UnitTest\ItopTestCase;
+use Symfony\Component\Mailer\Transport\Smtp\EsmtpTransport;
 use Symfony\Component\Mime\Part\DataPart;
 use Symfony\Component\Mime\Part\Multipart\AlternativePart;
 use Symfony\Component\Mime\Part\Multipart\RelatedPart;
@@ -298,4 +299,63 @@ HTML;
 			],
 		];
 	}
+
+	/**
+	 * @dataProvider provideCreateSmtpTransportSslOptions
+	 */
+	public function testCreateSmtpTransportSslOptions(string $sDsn, bool $bVerifyPeer, array $aExpectedSslOptions): void
+	{
+		$oEmail = new EMailSymfony();
+		/** @var EsmtpTransport $oTransport */
+		$oTransport = $this->InvokeNonPublicMethod(EMailSymfony::class, 'CreateSmtpTransport', $oEmail, [$sDsn, $bVerifyPeer]);
+
+		$aActualSslOptions = $oTransport->getStream()->getStreamOptions()['ssl'] ?? [];
+
+		$this->assertSame($aExpectedSslOptions, $aActualSslOptions);
+	}
+
+	public function provideCreateSmtpTransportSslOptions(): array
+	{
+		$aDisabledVerification = [
+			'verify_peer'      => false,
+			'verify_peer_name' => false,
+			'allow_self_signed' => true,
+		];
+
+		return [
+			// Regression scenario (N°9584): STARTTLS starts the connection unencrypted, so the 'ssl' key
+			// is absent from stream options at construction time. verify_peer=false must still be applied.
+			'STARTTLS, verify_peer=false' => [
+				'smtp://localhost:587?encryption=starttls',
+				false,
+				$aDisabledVerification,
+			],
+			'implicit TLS (smtps), verify_peer=false' => [
+				'smtps://localhost:465',
+				false,
+				$aDisabledVerification,
+			],
+			'plain SMTP, verify_peer=false' => [
+				'smtp://localhost:25',
+				false,
+				$aDisabledVerification,
+			],
+			// Default behavior: verify_peer=true must leave stream options untouched (empty).
+			'STARTTLS, verify_peer=true (default)' => [
+				'smtp://localhost:587?encryption=starttls',
+				true,
+				[],
+			],
+			'implicit TLS (smtps), verify_peer=true (default)' => [
+				'smtps://localhost:465',
+				true,
+				[],
+			],
+			'plain SMTP, verify_peer=true (default)' => [
+				'smtp://localhost:25',
+				true,
+				[],
+			],
+		];
+	}
 }