How to Fix Microsoft 365 Error 550 5.7.705 (Tenant Abuse)
Question details
Users are unable to send outbound emails due to a tenant-level block restricting the service.
- Product
- Microsoft 365
- Device & OS
- not provided
- Scenario
- Attempting to send outbound emails through Microsoft 365 Exchange after the account or tenant has been flagged for spam or exceeded sending limits.
- Observed behavior
- Outbound emails are completely blocked, and the system returns a non-delivery report (NDR) containing Error 550 5.7.705.
Ensure you have Microsoft 365 global or Exchange administrator privileges, as resolving a tenant-level block requires access to security settings and the ability to submit administrative support tickets.
Secure the Microsoft 365 Tenant and Remove Threats
Before requesting Microsoft to unblock your outbound mail, you must eliminate the source of the spam or unauthorized access to prevent further blocks.
If a tenant exceeds its sending limit due to compromised accounts or unauthorized connectors, Microsoft will block outbound mail to protect its network reputation. You must comprehensively secure the environment first.
Identify any suspected compromised accounts in the Microsoft 365 Admin Center and force a password reset for those users immediately.
Navigate to the active users section and enforce MFA for all accounts to prevent unauthorized access from stolen credentials.
Open the Exchange Admin Center, go to Mail flow > Connectors, and delete any unknown or unauthorized inbound/outbound connectors. Check for unauthorized inbox forwarding rules.
Use the message trace tool in the Exchange Admin Center to identify exactly which accounts were sending the spam and verify the threat is neutralized.
Raise a Support Ticket via the Admin Center
Once the tenant is secure, contact Microsoft Support directly through the Admin Portal to request a review of your tenant's outbound mail access.
Request a Callback via the Windows Get Help App
If you cannot access the admin portal or prefer desktop support, use the built-in Windows Get Help app to request a callback.
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Frequently Asked Questions
What does Error 550 5.7.705 indicate in Microsoft 365?
This error means your Microsoft 365 tenant has been blocked from sending outbound emails because it exceeded sending limits. This typically happens when compromised accounts or unauthorized connectors are used to send massive volumes of spam.
Will the email sending threshold be reset automatically after a month?
No, the block is not lifted automatically. Once your tenant is blocked for abuse, an administrator must secure the environment and proactively contact Microsoft support to manually review and remove the restriction.
Who can submit a ticket to fix this tenant abuse email block?
Only a designated administrator representative for your company's Microsoft 365 account has the required permissions to access the Microsoft 365 Admin Center and submit a support ticket to unblock outbound mail.
How do I identify which account is sending spam and causing the block?
You can identify compromised accounts by running a message trace in the Exchange Admin Center. Look for abnormal spikes in outbound messages, suspicious recipients, or unknown forwarding rules attached to specific users.
