diff --git a/lib/private/Mail/Mailer.php b/lib/private/Mail/Mailer.php
index e31784db58..6808892024 100644
--- a/lib/private/Mail/Mailer.php
+++ b/lib/private/Mail/Mailer.php
@@ -45,11 +45,11 @@ use OCP\IL10N;
 use OCP\ILogger;
 use OCP\IURLGenerator;
 use OCP\L10N\IFactory;
+use OCP\Mail\Events\BeforeMessageSent;
 use OCP\Mail\IAttachment;
 use OCP\Mail\IEMailTemplate;
 use OCP\Mail\IMailer;
 use OCP\Mail\IMessage;
-use OCP\Mail\Events\BeforeMessageSent;
 
 /**
  * Class Mailer provides some basic functions to create a mail message that can be used in combination with
@@ -293,6 +293,15 @@ class Mailer implements IMailer {
 			$transport->setStreamOptions($streamingOptions);
 		}
 
+		$overwriteCliUrl = parse_url(
+			$this->config->getSystemValueString('overwrite.cli.url', ''),
+			PHP_URL_HOST
+		);
+
+		if (!empty($overwriteCliUrl)) {
+			$transport->setLocalDomain($overwriteCliUrl);
+		}
+
 		return $transport;
 	}
 
diff --git a/tests/lib/Mail/MailerTest.php b/tests/lib/Mail/MailerTest.php
index a11a1ab091..335f373f8c 100644
--- a/tests/lib/Mail/MailerTest.php
+++ b/tests/lib/Mail/MailerTest.php
@@ -22,8 +22,8 @@ use OCP\ILogger;
 use OCP\IURLGenerator;
 use OCP\L10N\IFactory;
 use OCP\Mail\Events\BeforeMessageSent;
-use Test\TestCase;
 use Swift_SwiftException;
+use Test\TestCase;
 
 class MailerTest extends TestCase {
 	/** @var IConfig|\PHPUnit\Framework\MockObject\MockObject */
@@ -218,4 +218,42 @@ class MailerTest extends TestCase {
 		$mailer = self::invokePrivate($this->mailer, 'getInstance');
 		$this->assertEquals(0, count($mailer->getTransport()->getStreamOptions()));
 	}
+
+	public function testLocalDomain(): void {
+		$this->config->method('getSystemValue')
+			->willReturnMap([
+				['mail_smtpmode', 'smtp', 'smtp']
+			]);
+		$this->config->method('getSystemValueString')
+			->with('overwrite.cli.url', '')
+			->willReturn('https://some.valid.url.com:8080');
+
+		/** @var \Swift_Mailer $mailer */
+		$mailer = self::invokePrivate($this->mailer, 'getInstance');
+		self::assertInstanceOf(\Swift_Mailer::class, $mailer);
+
+		/** @var \Swift_Transport_EsmtpTransport $transport */
+		$transport = $mailer->getTransport();
+		self::assertInstanceOf(\Swift_Transport_EsmtpTransport::class, $transport);
+		self::assertEquals('some.valid.url.com', $transport->getLocalDomain());
+	}
+
+	public function testLocalDomainInvalidUrl(): void {
+		$this->config->method('getSystemValue')
+			->willReturnMap([
+				['mail_smtpmode', 'smtp', 'smtp']
+			]);
+		$this->config->method('getSystemValueString')
+			->with('overwrite.cli.url', '')
+			->willReturn('https:only.slash.does.not.work:8080');
+
+		/** @var \Swift_Mailer $mailer */
+		$mailer = self::invokePrivate($this->mailer, 'getInstance');
+		self::assertInstanceOf(\Swift_Mailer::class, $mailer);
+
+		/** @var \Swift_Transport_EsmtpTransport $transport */
+		$transport = $mailer->getTransport();
+		self::assertInstanceOf(\Swift_Transport_EsmtpTransport::class, $transport);
+		self::assertEquals('[127.0.0.1]', $transport->getLocalDomain());
+	}
 }