diff --git a/lib/Migration/Version4002Date20250501195008.php b/lib/Migration/Version4002Date20250501195008.php
index fb82e9ea..95727b37 100644
--- a/lib/Migration/Version4002Date20250501195008.php
+++ b/lib/Migration/Version4002Date20250501195008.php
@@ -45,6 +45,7 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 			'length' => 64,
 			'default' => '',
 		]);
+		$table->addIndex(['email'], 'guests_users_email');
 		return $schema;
 	}
 
diff --git a/lib/UserBackend.php b/lib/UserBackend.php
index 1179434a..de51da50 100644
--- a/lib/UserBackend.php
+++ b/lib/UserBackend.php
@@ -229,6 +229,7 @@ public function getDisplayNames($search = '', $limit = null, $offset = null): ar
 				)
 				// sqlite doesn't like re-using a single named parameter here
 				->where($query->expr()->iLike('uid', $query->createPositionalParameter('%' . $this->dbConn->escapeLikeParameter($search) . '%')))
+				->orWhere($query->expr()->iLike('email', $query->createPositionalParameter('%' . $this->dbConn->escapeLikeParameter($search) . '%')))
 				->orWhere($query->expr()->iLike('displayname', $query->createPositionalParameter('%' . $this->dbConn->escapeLikeParameter($search) . '%')))
 				->orWhere($query->expr()->iLike('configvalue', $query->createPositionalParameter('%' . $this->dbConn->escapeLikeParameter($search) . '%')))
 				->orderBy($query->func()->lower('displayname'), 'ASC')
@@ -294,6 +295,11 @@ public function checkPassword(string $loginName, string $password) {
 				$qb->expr()->eq(
 					'uid_lower', $qb->createNamedParameter(mb_strtolower($loginName))
 				)
+			)
+			->orWhere(
+				$qb->expr()->eq(
+					'email', $qb->createNamedParameter($loginName)
+				)
 			);
 		$result = $qb->executeQuery();
 		$row = $result->fetch();
@@ -339,6 +345,11 @@ private function loadUser($uid): bool {
 					$qb->expr()->eq(
 						'uid_lower', $qb->createNamedParameter(mb_strtolower($uid))
 					)
+				)
+				->orWhere(
+					$qb->expr()->eq(
+						'email', $qb->createNamedParameter($uid)
+					)
 				);
 			$result = $qb->executeQuery();
 			$row = $result->fetch();
diff --git a/tests/unit/UserBackendTest.php b/tests/unit/UserBackendTest.php
index 423921e1..2e211e5c 100644
--- a/tests/unit/UserBackendTest.php
+++ b/tests/unit/UserBackendTest.php
@@ -70,4 +70,21 @@ public function testNoListing(): void {
 
 		$this->assertEquals([], $this->backend->getUsers());
 	}
+
+	public function testHashedUid(): void {
+		$email = 'foo@example.tld';
+		$uid = hash('sha256', $email);
+		$this->backend->createUser($uid, 'bar');
+		$this->backend->setInitialEmail($uid, $email);
+		$this->backend->setDisplayName($uid, 'foo');
+		$this->assertTrue($this->backend->userExists($email));
+
+		$this->assertEquals($uid, $this->backend->checkPassword($email, 'bar'));
+
+		$this->assertEquals('foo', $this->backend->getDisplayName($uid));
+		$this->assertEquals('foo', $this->backend->getDisplayName($email));
+		$this->assertEquals(['foo'], array_values($this->backend->getDisplayNames($uid)));
+		$this->assertEquals(['foo'], array_values($this->backend->getDisplayNames($email)));
+		$this->assertEquals(['foo'], array_values($this->backend->getDisplayNames(substr($email, 0, 10))));
+	}
 }