diff --git a/memento-note/lib/mail.ts b/memento-note/lib/mail.ts
index 409180f..3ab6222 100644
--- a/memento-note/lib/mail.ts
+++ b/memento-note/lib/mail.ts
@@ -61,8 +61,9 @@ async function sendViaResend(apiKey: string, { to, subject, html, attachments }:
     const { Resend } = await import('resend');
     const resend = new Resend(apiKey);
 
-    const from = process.env.NEXTAUTH_URL
-      ? `Memento <noreply@${new URL(process.env.NEXTAUTH_URL).hostname}>`
+    const hostname = process.env.NEXTAUTH_URL ? new URL(process.env.NEXTAUTH_URL).hostname : '';
+    const from = hostname && hostname !== 'localhost'
+      ? `Memento <noreply@${hostname}>`
       : 'Memento <onboarding@resend.dev>';
 
     // Resend supports attachments with inline content