diff --git a/content/showArticle.php b/content/showArticle.php
index d6a85c6..6b6a7b1 100644
--- a/content/showArticle.php
+++ b/content/showArticle.php
@@ -15,15 +15,17 @@ $userManager = UserManager::getInstance();
  */
 function getCommentAuthorName($email, $userManager)
 {
+    $email = trim($email);
     $user = $userManager->findUser($email);
 
     if ($user === null) {
         return $email;
     }
 
-    $fullName = trim(
-            ($user["vorname"] ?? "") . " " . ($user["nachname"] ?? "")
-    );
+    $vorname = trim($user["vorname"] ?? "");
+    $nachname = trim($user["nachname"] ?? "");
+
+    $fullName = trim($vorname . " " . $nachname);
 
     return $fullName !== "" ? $fullName : $email;
 }
diff --git a/php/model/DatabaseUserManager.php b/php/model/DatabaseUserManager.php
index 8a7cc47..bfe674d 100644
--- a/php/model/DatabaseUserManager.php
+++ b/php/model/DatabaseUserManager.php
@@ -75,11 +75,15 @@ class DatabaseUserManager implements UserManagerDAO {
         try {
             $db = $this->getConnection();
 
-            $sql = "SELECT * FROM users WHERE email = :email";
+            $sql = "
+            SELECT *
+            FROM users
+            WHERE LOWER(TRIM(email)) = LOWER(TRIM(:email))
+               ";
             $command = $db->prepare($sql);
 
             $command->execute([
-                ":email" => $email
+                ":email" => trim($email)
             ]);
 
             $user = $command->fetch(PDO::FETCH_ASSOC);