# SMTP: 553 5.7.1 <noreply@example.com>: Sender address rejected: not owned by user user@example.com

**Code:** `553 5.7.1 Sender address rejected: not owned by user` · **Category:** Email / SMTP · **Seen on:** SMTP, Linux

The SMTP server only lets an authenticated user send as addresses they own, and the From/envelope sender does not match the login.

## Meaning

Servers enforce `reject_sender_login_mismatch` (Postfix) or equivalent so users cannot spoof others. Use the same address you log in with, or add the alias to that account. Gmail does the same: you must add "Send mail as" aliases and verify them.

## Common causes

- MAIL FROM differs from the authenticated user
- Missing alias or "send as" permission
- Application using a generic noreply@ address with a personal account
- Postfix `smtpd_sender_login_maps` does not include the address

## Quick fix

1. Send from the address you authenticate with
2. Add the address as an alias or "Send mail as" identity
3. Postfix: map the alias in `smtpd_sender_login_maps`

## Detailed fix by platform

### Postfix

1. `smtpd_sender_restrictions = reject_sender_login_mismatch` and `smtpd_sender_login_maps = hash:/etc/postfix/sender_login` with `noreply@example.com user@example.com`; then `postmap` and reload

## How to diagnose

1. **From** — Matches the login?
2. **Alias** — Registered?
3. **Rule** — Server sender restrictions?

---
Source: [WhatIsMyError](https://whatismyerror.com/errors/email/553-5-7-1-sender-not-owned)