Can not send mails, due to (not possible) exceeding of limits

Question

At our [Moderator note: personal info removed] maildomain, we get this message:

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)

But we did not exceed the 10,000 limit in any way. So how can this happen and how can we solve it?

Answer 1

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Hi @Abel Keun

Thank you for posting your question in the Microsoft Q&A forum.  

Looks like  you’re running into the Tenant External Recipient Rate Limit (TERRL) in Exchange Online. 

This is a tenant‑wide sending limit that caps how many external recipients your entire tenant can send email to within a rolling 24‑hour window. External recipients include any address outside your accepted domains. TERRL counts the total number of external recipient addresses processed (recipient instances), across all users, shared mailboxes, apps, automated flows, or systems sending through Exchange Online. 

If the limit displays as 0 or seems abnormally low: 

This value is not configurable through the admin portal or PowerShell, TERRL cannot be modified via Set‑TransportConfig or any similar cmdlet. The limit is calculated automatically by Microsoft based on the number of valid, paid (non‑trial) Exchange Online or Microsoft 365 licenses in your tenant. 

To increase the limit: 

You could consider to add more paid Microsoft 365 or Exchange Online licenses, the TERRL increases according to Microsoft’s formula. If the tenant is in trial mode or uses only trial licenses, the limit is fixed at a lower level (typically 5,000 per day). Upgrading to paid licenses resolves this. 

You can refer via: Introducing Exchange Online Tenant Outbound Email Limits | Microsoft Community Hub 

To resolve your case more accurately, Microsoft’s support team will need to assist. A technical support engineer can perform a remote session to investigate the situation, verify the backend configurations, and run any necessary synchronization tools to resolve the problem. If the issue requires further attention, they can escalate it to a specialized team for deeper analysis.     

Reference: Reference: Get support - Microsoft 365 admin | Microsoft Learn 

Note: To create a support ticket, you need to have Microsoft 365 admin privileges and if you aren’t admin of your organization, please contact the admin of creating a new ticket.  

Apologies for redirecting you to the related development team support as the moderators in this community have limited resources to check the backend information, and to get the fast and better assistance we requested for it.  

If you have any additional concerns, feel free to comment below. I would be more than happy to assist. 

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Answer 2

Our limit is set on 0.

That should be 10,000. How to change?

Answer 3

The total number of sent mails in 24 hour is only 82.

How can we still get this message of exceeding the limit, as 82 is largely wtihin this limit

Answer 4

The error indicates that the tenant-wide external recipient limit (TERRL) was exceeded, not the per‑mailbox 10,000‑recipients‑per‑day limit.

Key points from the service behavior:

1. There are multiple different limits
   • Per-mailbox recipient rate limit: 10,000 recipients per 24‑hour sliding window. Exceeding this gives errors like 5.1.90 or 5.2.2 (submission quota exceeded).
   • Tenant External Recipient Rate Limit (TERRL): maximum number of external recipients the entire tenant can send to in a 24‑hour sliding window. This is what generates error 5.7.233.
   • TERRL is not a fixed 10,000; it depends on the number of licenses in the tenant. Trial tenants have a much lower cap (5,000 external recipients per day).
2. How the tenant external limit is counted
   • External recipients are any addresses whose domain is not configured as an accepted domain in the tenant.
   • Distribution groups are expanded and each external member is counted individually. For example, sending one message to a group with 1,000 external members counts as 1,000 external recipients.
   • Counting happens after all group and nested group expansion.
   • The limit is enforced over a 24‑hour sliding window. Once the total external recipients sent to in the last 24 hours drops below the tenant limit, sending resumes automatically.
3. Why it can trigger even if no one thinks they sent that much mail
   • Multiple users or applications in the tenant may be sending to external recipients, and their totals are aggregated.
   • Use of large distribution lists or nested groups with many external members can quickly consume the tenant quota even with a small number of messages.
   • Automated systems, workflows, or compromised accounts can send large volumes without being obvious to end users.
4. How to verify and diagnose
   • An admin can check the tenant’s actual TERRL value and current usage in the Exchange admin center (EAC) under Reports → Mail flow → Tenant Outbound External Recipients.
   • If users are seeing NDRs with code 5.7.233, that confirms the tenant external recipient rate limit is what’s being hit.
   • If the NDR shows 5.1.90 or 5.2.2, that indicates the per‑mailbox recipient or message rate limits instead.
5. How to resolve and prevent recurrence
   • Short term: wait until the 24‑hour sliding window moves forward and the total external recipients sent to falls below the tenant limit; sending will resume automatically.
   • Review who/what is sending:
     • Identify high‑volume senders (users, shared mailboxes, apps, workflows) and reduce external bulk mail from Exchange Online.
     • Check for compromised accounts if the volume is unexpected, following the guidance in “Responding to a compromised account.”
   • For scenarios that legitimately require high‑volume external sending, use a service designed for bulk email rather than Exchange Online. Microsoft recommends Azure Communication Services email for bulk or high‑volume external emailing.

If the tenant is a trial tenant, be aware that the TERRL is capped at 5,000 external recipients per day, which is easier to hit than the standard production limits.

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References:

• Email non-delivery reports and SMTP errors in Exchange Online
• Fix NDR error "the sender's submission quota was exceeded" in Exchange Online
• Exchange Online limits