diff --git a/lib/private/Mail/Mailer.php b/lib/private/Mail/Mailer.php
index f8dc739428..2e996dea50 100644
--- a/lib/private/Mail/Mailer.php
+++ b/lib/private/Mail/Mailer.php
@@ -221,6 +221,10 @@ class Mailer implements IMailer {
 	 * @return bool True if the mail address is valid, false otherwise
 	 */
 	public function validateMailAddress(string $email): bool {
+		if ($email === '') {
+			// Shortcut: empty addresses are never valid
+			return false;
+		}
 		$validator = new EmailValidator();
 		$validation = new RFCValidation();
 
diff --git a/tests/lib/Mail/MailerTest.php b/tests/lib/Mail/MailerTest.php
index 3ec2e96dfa..a11a1ab091 100644
--- a/tests/lib/Mail/MailerTest.php
+++ b/tests/lib/Mail/MailerTest.php
@@ -178,6 +178,7 @@ class MailerTest extends TestCase {
 			['lukas@192.168.1.1', true],
 			['lukas@éxämplè.com', true],
 			['asdf', false],
+			['', false],
 			['lukas@owncloud.org@owncloud.com', false],
 		];
 	}