5.7.12: recipient accepts mail only from its organization
The address you wrote to takes mail only from inside its own organization, so outside senders are refused until that organization's admin changes the setting.
- Microsoft
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 5.7.12
- 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
5.7.12 Sender was not authenticated by organization
What it means
With 5.7.12, the address you wrote to accepts only senders from its own organization, so an outside sender counts as unauthenticated and is turned away. Microsoft lists related codes for specific kinds of recipient: 5.7.133 for groups, 5.7.134 for mailboxes, 5.7.13 or 5.7.135 for public folders and 5.7.136 for mail users. The restriction lives on the recipient side, so the sender cannot lift it; that organization's email admin can.
Common causes
- The recipient requires senders to be authenticated, which blocks everyone outside the organization.
- The address is meant for internal use only, such as a staff list or an internal service address.
How to fix it
- 01Contact the recipient by another channel and ask whether the address should accept outside mail.
- 02If it should, their admin can remove the sender authentication requirement or add you to its allowed senders.
- 03If it should not, use the public contact address they give you instead.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Email nondelivery reports and SMTP errors in Exchange Onlinelearn.microsoft.com
Related codes
- 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.
- 550 5.7.134Mailbox rejects mail from outside the organization.The recipient mailbox is set to accept only authenticated senders, so mail from outside its organization is rejected.
- 550 5.7.135Public folder rejects mail from outside.The recipient is a mail-enabled public folder set to reject messages from senders outside its organization.
- 550 5.7.136Mail user rejects mail from outside.The recipient is a mail user set to reject messages from senders outside its organization.
Further reading
All 111 Microsoft codesEvery code in the wikiPaste your own bounce