550 5.7.1: not authorized to send to this recipient
You do not have permission to send to this recipient, typically a group restricted to certain senders or a recipient protected by a mail flow rule.
- Microsoft
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550 5.7.1
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The recipient's side. Their mail admin has to change something; you can tell them.
- What the server says
550 5.7.1 Delivery not authorized
What it means
5.7.1 is Exchange Online's general permission error, and Microsoft's guidance for it also applies to 5.7.0 to 5.7.999 when nothing more specific exists. The Delivery not authorized form means a security setting stopped the message: the recipient, often a distribution group, accepts mail only from members or listed senders, or a transport rule matched the message and rejected it. Groups with more than 5,000 members also require moderator approval. The sender cannot change the setting; the group owner or the recipient's admin has to grant permission.
Common causes
- The recipient is a group that accepts messages only from its members or an allowed senders list.
- A mail flow (transport) rule on the recipient side rejected the message.
- The recipient accepts mail only from inside its organization.
- The group has more than 5,000 members and requires moderator approval.
How to fix it
- 01If the recipient is a group in your organization, ask its owner (shown in Outlook) to add you to its allowed senders or to the group.
- 02If the recipient is external, contact them by another channel and ask their admin to accept mail from you.
- 03Group owners: add the sender to the allowed senders list, using a mail contact for external senders, or allow external senders.
- 04Admins: check mail flow rules that restrict senders and adjust them.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Fix NDR error "550 5.7.1" in Exchange Onlinelearn.microsoft.com
- Email nondelivery reports and SMTP errors in Exchange Onlinelearn.microsoft.com
Related codes
- 550 5.7.124Sender not in the group's allowed senders.The distribution group accepts mail only from listed senders, and you are not on its list, directly or through a group.
- 550 5.7.133Group rejects mail from outside the organization.The recipient is a distribution group set to reject messages from senders outside its organization.
- 5.7.1Delivery not authorised.The receiving server refuses the message because this sender is not allowed to send to this recipient, as a result of filtering by host or by recipient.
5.7.1 at other providers
- 550 5.7.1Blocked by a domain policy.A rule set by the recipient's or the sender's Google Workspace admin blocks this message, so Gmail rejected it under that policy.
- 550 5.7.1Relay IP does not match the sending domain.Google's SMTP relay knows your IP, but the mail's sending domain is not one that IP is registered to relay for in your Workspace account.
- 550 5.7.1Blocked as likely spam.Gmail's filters judged this message likely to be spam and rejected it outright, instead of delivering it to the spam folder.
- 550 5.7.1IPv6 sender without PTR or authentication.Gmail rejected mail that arrived over IPv6 because the sending address lacks a matching PTR record, or the message failed authentication.
- 550 5.7.1Blocked for low IP reputation.Gmail permanently rejected the message because the IP it came from has a very low reputation with Gmail.
- 550 5.7.1Blocked for low domain reputation.Gmail permanently rejected the message because the domain it comes from has a very low reputation with Gmail.
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