diff --git a/index.js b/index.js
index 01eae24..edc8c0d 100644
--- a/index.js
+++ b/index.js
@@ -18,12 +18,20 @@ const app = express();
   }); 
 
 app.get('/signup', async (req, res) => {
-  const { email, callsign } = req.query
+  var { email, callsign } = req.query
   res.set("Access-Control-Allow-Origin", "*")
   if (!email) return res.json({ success: false, error: "Please provide an error" })
   if (!callsign) return res.json({ success: false, error: "Please provide a callsign" })
   if (!validator.isEmail(email)) return res.json({ success: false, error: "Please provide a (valid) email" })
   if (callsign.length > 7 || callsign.length < 3) return res.json({ success: false, error: "Please provide a (valid) callsign" })
+  callsign = callsign.toLowerCase()
+  var a = request('GET', 'https://mail.email.radio/api/v1/get/mailbox/all/email.radio', {
+  headers: {
+    'Content-Type': "application/json",
+    'X-API-Key': process.env.MAILCOW_API_KEY,
+  }}).getBody("utf8")
+  var boxes = JSON.parse(a)
+  if (boxes.find(box=>box.local_part == callsign.toLowerCase())) return res.json({ success: false, error: "There is already someone using this callsign. If someone is using your callsign, please email postmaster@email.radio" })
   await transporter.sendMail({
     from: process.env.SYSTEM_USERNAME, // sender address
     to: email, // list of receivers