diff --git a/supabase/functions/send-smtp-email/index.ts b/supabase/functions/send-smtp-email/index.ts
index 24c5f0a..802b466 100644
--- a/supabase/functions/send-smtp-email/index.ts
+++ b/supabase/functions/send-smtp-email/index.ts
@@ -62,11 +62,25 @@ Deno.serve(async (req) => {
       return json({ error: "to and subject are required" }, 400);
     }
 
+    // Auto-correct common TLS misconfigurations:
+    // - Port 465 always uses implicit TLS (tls: true)
+    // - Port 587 / 25 use STARTTLS (tls: false; denomailer upgrades automatically)
+    let useTls = !!settings.secure;
+    if (settings.port === 465) useTls = true;
+    else if (settings.port === 587 || settings.port === 25) useTls = false;
+
+    console.log("SMTP connecting", {
+      host: settings.host,
+      port: settings.port,
+      tls: useTls,
+      hasAuth: !!settings.username,
+    });
+
     const client = new SMTPClient({
       connection: {
         hostname: settings.host,
         port: settings.port,
-        tls: !!settings.secure,
+        tls: useTls,
         auth: settings.username
           ? { username: settings.username, password }
           : undefined,