diff --git a/src/app/Auth/LDAPUserProvider.php b/src/app/Auth/LDAPUserProvider.php
--- a/src/app/Auth/LDAPUserProvider.php
+++ b/src/app/Auth/LDAPUserProvider.php
@@ -22,7 +22,7 @@
      */
     public function retrieveByCredentials(array $credentials)
     {
-        $entries = User::where('email', '=', $credentials['email'])->get();
+        $entries = User::where('email', \strtolower($credentials['email']))->get();
 
         $count = $entries->count();
 
@@ -51,7 +51,7 @@
     {
         $authenticated = false;
 
-        if ($user->email == $credentials['email']) {
+        if ($user->email === \strtolower($credentials['email'])) {
             if (!empty($user->password)) {
                 if (Hash::check($credentials['password'], $user->password)) {
                     $authenticated = true;
diff --git a/src/tests/Feature/Controller/AuthTest.php b/src/tests/Feature/Controller/AuthTest.php
--- a/src/tests/Feature/Controller/AuthTest.php
+++ b/src/tests/Feature/Controller/AuthTest.php
@@ -110,6 +110,16 @@
         $this->assertEquals(\config('jwt.ttl') * 60, $json['expires_in']);
         $this->assertEquals('bearer', $json['token_type']);
 
+        // Valid user+password (upper-case)
+        $post = ['email' => 'John@Kolab.org', 'password' => 'simple123'];
+        $response = $this->post("api/auth/login", $post);
+        $json = $response->json();
+
+        $response->assertStatus(200);
+        $this->assertTrue(!empty($json['access_token']));
+        $this->assertEquals(\config('jwt.ttl') * 60, $json['expires_in']);
+        $this->assertEquals('bearer', $json['token_type']);
+
         // TODO: We have browser tests for 2FA but we should probably also test it here
 
         return $json['access_token'];