diff --git a/memento-note/lib/mail.ts b/memento-note/lib/mail.ts
index 3ab6222..1b10a71 100644
--- a/memento-note/lib/mail.ts
+++ b/memento-note/lib/mail.ts
@@ -61,10 +61,22 @@ async function sendViaResend(apiKey: string, { to, subject, html, attachments }:
     const { Resend } = await import('resend');
     const resend = new Resend(apiKey);
 
-    const hostname = process.env.NEXTAUTH_URL ? new URL(process.env.NEXTAUTH_URL).hostname : '';
-    const from = hostname && hostname !== 'localhost'
-      ? `Memento <noreply@${hostname}>`
-      : 'Memento <onboarding@resend.dev>';
+    // Use explicitly configured from address if available
+    const configuredFrom = process.env.SMTP_FROM || process.env.RESEND_FROM || '';
+    let from: string;
+    if (configuredFrom) {
+      // Wrap in display name if it's a plain email
+      from = configuredFrom.includes('<') ? configuredFrom : `Memento <${configuredFrom}>`;
+    } else {
+      const rawUrl = process.env.NEXTAUTH_URL || '';
+      let hostname = '';
+      try { hostname = rawUrl ? new URL(rawUrl).hostname : ''; } catch {}
+      // IP addresses and localhost are not valid email domains for Resend
+      const isIP = /^[\d.]+$/.test(hostname);
+      from = hostname && hostname !== 'localhost' && !isIP
+        ? `Memento <noreply@${hostname}>`
+        : 'Memento <onboarding@resend.dev>';
+    }
 
     // Resend supports attachments with inline content
     const resendAttachments = attachments?.map(att => ({