SMTP error X.7.1
Delivery not authorized
Updated Jul 1, 2026
Delivery was refused on policy — the address is fine, but the server would not accept your mail. Usually a blocklist, failed authentication (SPF/DKIM/DMARC), or a spam signal. Fix your sender reputation, then resend.
Check authentication, reputation, allowlists, and recipient policy
What it means
X.7.1 (“Delivery not authorized, message refused”) is a security/policy rejection. Unlike X.1.1, the mailbox exists — the receiver chose not to accept your message. As 5.7.1 it is permanent; the cause is on your side or your infrastructure’s.
Common causes
Your sending IP or domain appears on a blocklist the receiver honors.
SPF, DKIM, or DMARC did not pass, so the receiver treated the mail as unauthorized.
The message tripped a policy or content rule.
You are not authorized to send as this sender from this source.
How to fix it
- Check blocklists for your IP and domain
A listing is the most direct cause. If listed, follow each list’s delisting process after fixing the underlying issue.
- Fix SPF, DKIM, and DMARC
Publish all three, ensure your sending source is included, and confirm they pass on a test send.
- Review recent sending
Spam complaints, sudden volume spikes, or dead-address bounces damage reputation and trigger 5.7.1. Tighten list hygiene.
- Warm up the domain
Policy blocks hit cold or low-trust senders hardest. Build a positive sending history so receivers accept your mail.
Common questions
The address works for others — why am I blocked?
5.7.1 is about your sender reputation and authentication, not the recipient. The same address accepts mail from trusted senders and refuses it from listed or unauthenticated ones.