Microsoft (Outlook.com and Microsoft 365) · permanent error
550 5.7.703: recipient blocked by your Tenant Allow/Block List
Someone in your organization sent to an address or domain that your own Tenant Allow/Block List blocks, so the whole message was stopped.
- Microsoft
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550 5.7.703
- 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 sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
550 5.7.703 Your message can't be delivered because messages to XXX, YYY are blocked…
What it means
The Tenant Allow/Block List in Microsoft 365 can block senders and recipients by address or domain. When a user sends to an address or domain that has a block entry, Exchange Online refuses the message with 550 5.7.703. The block applies to the whole message: every other recipient, internal or external, misses it too, even if only one address matched. The list belongs to the sender's own organization, so only its admin can change it.
Common causes
- An admin added the recipient address or domain to the Tenant Allow/Block List as a block entry.
- A block entry for a whole domain caught an address that should be allowed.
How to fix it
- 01Tell your email admin which recipient was blocked.
- 02Admins: review the block entries for the address or domain in the Tenant Allow/Block List in the Microsoft Defender portal.
- 03Remove or narrow the entry if the block is not intended, then resend to everyone.
- 04If the block is intended, resend the message without that recipient.
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 codes 550 5.7.703, 550 5.7.705, 550 5.7.708, and 550 5.7.750learn.microsoft.com
- Manage allows and blocks in the Tenant Allow/Block Listlearn.microsoft.com
- Email nondelivery reports and SMTP errors in Exchange Onlinelearn.microsoft.com
Related codes
Further reading
All 111 Microsoft codesEvery code in the wikiPaste your own bounce