Error guide / 550 5.7.1 Message rejected

The 550 5.7.1 rejected error

The 550 5.7.1 code means the recipient's server accepted the connection but refused to deliver your message for policy or security reasons. It is a permanent (hard) rejection, so retrying will not help until the cause is fixed. It is most often triggered by mail without proper authentication, poor IP reputation, or messages that look like spam.

What causes it

There are several causes: SPF/DKIM/DMARC are not set up, the sender IP or domain is on a blacklist, or the server tries to send mail for domains it does not own (relaying denied). The sender side is usually at fault, less often an overly strict recipient policy.

How to fix it

1. Read the full rejection text: after 5.7.1 there is often a hint (policy, blocked, relaying denied).
2. Set up SPF, DKIM and DMARC for your domain, since big providers often return 550 5.7.1 without them.
3. Check your server IP against blacklists and request delisting if needed.
4. If it says relaying denied, send through authenticated SMTP instead of directly.
5. For bulk mail, warm up the domain gradually and never send to purchased lists.
6. Check your domain authentication with the tool below and fix whatever fails.

Related errors

• 550 SPF check failed The 550 SPF check failed error
• Листи потрапляють у спам Emails going to spam
• DMARC policy reject (p=reject) DMARC reject: message blocked by policy
• DKIM signature verification failed DKIM fail: signature does not verify