fix(mail): properly encode mail subject into utf8

functions.php

@@ -30,6 +30,19 @@ function validateEmail($email)
     return preg_match(EMAIL_REGEX, $email);
 }
 
+/**
+ * Encode email subject to handle umlauts and special characters (RFC 2047)
+ */
+function encodeEmailSubject($subject)
+{
+    // Check if subject contains non-ASCII characters
+    if (preg_match('/[^\x20-\x7E]/', $subject)) {
+        // Use RFC 2047 encoding: =?charset?encoding?encoded-text?=
+        return '=?UTF-8?B?' . base64_encode($subject) . '?=';
+    }
+    return $subject;
+}
+
 /**
  * Sanitize input string
  */
@@ -206,7 +219,7 @@ function sendEmail($subject, $xmlContent, $toEmail = null)
     $headers .= "Content-Type: application/xml; charset=UTF-8\r\n";
     $headers .= "X-Mailer: PHP/" . phpversion();
 
-    $result = mail($to, $subject, $xmlContent, $headers);
+    $result = mail($to, encodeEmailSubject($subject), $xmlContent, $headers);
 
     if ($result) {
         writeLog("Email sent successfully via mail()", 'SUCCESS');
@@ -253,7 +266,7 @@ function sendEmailSMTP($subject, $xmlContent, $to, $from)
 
             // Content - XML as body
             $mail->isHTML(false);
-            $mail->Subject = $subject;
+            $mail->Subject = encodeEmailSubject($subject);
             $mail->Body = $xmlContent;
             $mail->ContentType = 'text/plain';
 
@@ -387,7 +400,7 @@ function sendEmailSMTP($subject, $xmlContent, $to, $from)
         // Send email headers and body
         $headers = "From: {$from}\r\n";
         $headers .= "To: {$to}\r\n";
-        $headers .= "Subject: {$subject}\r\n";
+        $headers .= "Subject: " . encodeEmailSubject($subject) . "\r\n";
         $headers .= "Content-Type: text/plain; charset=UTF-8\r\n";
         $headers .= "X-Mailer: PHP/" . phpversion() . "\r\n";
         $headers .= "\r\n";