Exchange Online tenant outbound email limits (TERRL)
Overview
Section titled “Overview”The Tenant External Recipient Rate Limit (TERRL) is an Exchange Online policy that limits how many external recipients a Microsoft 365 tenant can send to in a 24-hour sliding window. It is in force for all worldwide tenants. Microsoft designed it to reduce outbound abuse of the service and keep performance consistent for all customers. It may mean new planning and tools for organizations that send large volumes of email, and the Exchange admin center reports your usage against the limit.
This article covers how the limit is calculated, where it applies, how to monitor it, and what happens if your tenant goes over it.
What is TERRL?
Section titled “What is TERRL?”TERRL caps the total number of external recipients that your whole tenant can email within a 24-hour sliding window.
- External recipients are any email addresses that are not in your tenant’s accepted domains, including recipients in other Microsoft 365 tenants.
- The limit is tenant-wide: it counts the messages sent by all users, and from on-premises servers that relay through your tenant.
- TERRL doesn’t track unique recipients. If you send 1,000 messages to the same external recipient in a day, that counts as 1,000.
- Distribution group members count one by one. A message to a group with 1,000 external members counts as 1,000 external recipients.
- The policy is separate from the existing per-mailbox limits, and is applied independently.
How the limit is calculated
Section titled “How the limit is calculated”For most tenants, the daily external recipient limit is based on the tenant’s email licenses (any Exchange Online or Exchange Online Protection license), using this formula:
500 * (number of non-trial email licenses ^ 0.7) + 9500
| Number of non-trial, non-EDU email licenses | Daily external recipient limit |
|---|---|
| 1 | 10,000 |
| 2 | 10,312 |
| 10 | 12,006 |
| 25 | 14,259 |
| 100 | 22,059 |
| 1,000 | 72,446 |
| 10,000 | 324,979 |
| 100,000 | 1,590,639 |
Trial, new, and education tenants
Section titled “Trial, new, and education tenants”Since September 2026, these tenants have lower limits:
- Trial tenants
- 500 external recipients per day, whatever their license count.
- New tenants
- 10% of the standard limit for the first 30 days, 25% for days 31 to 60, and the full limit after 60 days.
- Tenants with free EDU licenses
- Free education licenses, such as Microsoft 365 A1, count at a lower weight:
500 × (Purchased Email Licenses^0.7 + Free EDU Licenses^0.3) + 9500
Where TERRL applies
Section titled “Where TERRL applies”- Worldwide (WW) tenants
- Fully in force.
- GCC, GCC High, DoD, and 21Vianet
- Postponed. Microsoft will announce dates when they are final.
Monitoring your usage
Section titled “Monitoring your usage”
In the Exchange admin center
Section titled “In the Exchange admin center”Go to Reports > Mail flow > Tenant Outbound External Recipients Rate. The report shows:
- The total external recipients in the past 24 hours
- Your tenant’s current quota
- The percentage of the quota used
- The number of recipients blocked, if the limit was exceeded
- Whether enforcement is turned on
With PowerShell
Section titled “With PowerShell”Get-LimitsEnforcementStatusWhat happens when you exceed the limit
Section titled “What happens when you exceed the limit”Messages to external recipients are blocked, and senders get a non-delivery report (NDR) with one of these codes:
550 5.7.232- Trial tenants: the trial tenant exceeded its daily limit.
550 5.7.233- Non-trial tenants: the tenant exceeded its daily limit.
Sending resumes automatically when usage drops below the limit.
What doesn’t count toward TERRL
Section titled “What doesn’t count toward TERRL”- Journaling messages created by Exchange Online rules
- Automatic replies, such as out-of-office replies
- Delivery status notifications, such as NDRs, delivery receipts, and read receipts
- Azure Communication Services messages
- System notifications from Microsoft apps, such as Teams, SharePoint, and Yammer
- Messages from the Exchange Online High-Volume Email solution
Recommendations for high-volume sending
Section titled “Recommendations for high-volume sending”If your organization sends bulk or transactional messages, such as marketing, alerts, or notifications:
- Don’t rely only on Exchange Online mailboxes for that volume.
- Use Azure Communication Services or another dedicated high-volume email solution.
- Or buy more Exchange Online licenses to cover your sending volume.
What’s next
Section titled “What’s next”- Introducing Exchange Online Tenant Outbound Email Limits: Microsoft’s announcement and FAQ.
- How does Opensense work with Microsoft 365?: how Opensense routes email in Microsoft 365.