Email cant be sent because Tenant has exceeded its daily limit

Question

My emails have stopped sending today. I have not sent out many emails yet am receiving the follow error message - Remote server returned '550 5.7.233 - Your message can't be sent because your tenant has exceeded its daily limit for sending email to external recipients (tenant external recipient rate limit).

Answer 1

Dear @Gary Macdonald, 

Thank you for reaching out. I understand how disruptive it is when your emails suddenly stop sending. 

The error message indicates that your organization has reached Exchange Online’s daily limit for sending messages to external addresses. This limit applies to the entire tenant, not to an individual mailbox. Because of that, the error may appear even when your own activity is minimal, as the system counts all external messages sent by every account and automated process in the organization. 

Here are some options you can consider: 

Please note that these actions require an organization‑level IT administrator. If you are an end-user, please contact your IT admin and share this information with them. 

Option 1: Allow time for the limit to reset 

The restriction is based on a 24‑hour rolling window and is lifted automatically once older messages fall outside that timeframe. Many customers regain the ability to send external email once the volume naturally decreases. 

Option 2: Review recent sending activity 

If you or your IT administrator have access to the Exchange admin center, the following steps can help identify what triggered the spike: 

• Open the Exchange admin center, go to Reports, then Mail flow, and review the “Tenant Outbound External Recipients” report to see usage patterns. 

• Run a message trace for the past two or three days to check whether any mailbox or automated application sent an unusually high number of external messages. 

Option 3: Limit new external sending until the restriction clears 

Keeping external mail volume low for several hours gives the rolling window time to reset more quickly. This reduces the chance of the error reappearing. 

Exchange Online Tenant Outbound Email Limits

Option 4: Use recipient groups when sending to large audiences 

If you regularly contact many external addresses at once, sending to a distribution group or Microsoft 365 group counts as only one recipient at send time. This helps keep usage lower. 

Option 5: Consider alternatives for large‑scale external communication 

If the organization often needs to email high volumes of external recipients, a service designed for bulk email, such as Azure Communication Services Email or a dedicated marketing platform, may be more suitable. 

Note: This is additional information and not required unless your organization routinely sends large external campaigns. 

Option 6: Check for any account that might have been compromised 

If a mailbox suddenly sends a high volume of messages because it was compromised, the system may apply restrictions or alerts. Your administrator can review this in the Microsoft Defender portal under “Restricted entities”. 

As community moderators, we kindly ask for your understanding that our access to internal development details is limited. Our primary role is to guide users toward the appropriate resources and support channels. While we may not have visibility into performing deeper backend analysis, we’ll continue doing our best to support you within the scope of our responsibilities.  

I hope this information is helpful. If you have any questions or need further support, please don’t hesitate to reach out at any time. 

Thank you for your patience and understanding. 

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