Update Aug 13, 2026: To further strengthen protection against abuse and ensure fair use of Exchange Online resources, we are updating how the Tenant External Recipient Rate Limit (TERRL) quota is calculated for certain tenants. These changes will begin rolling out starting September 14, 2026. Also, TERRL rollout has been postponed for the following environments: GCC, GCCH, DoD, and 21Vianet.
As with all cloud services, Exchange Online imposes service limits to prevent misuse of Exchange Online resources and ensure availability for all users. For example, aside from the High-volume Email offering, Exchange Online doesn’t support bulk or high-volume email, yet until now we’ve mostly used only a per-mailbox daily send limit (known as the Recipient Rate Limit or RRL) to enforce this.
Going forward, we’re introducing new tenant-level outbound email limits (also known as the Tenant External Recipient Rate Limit or TERRL) that are calculated based on the number of email licenses a tenant has or if a tenant has only trial licenses. Enforcement for trial-only and single-seat tenants is already enabled. We’ll continue to enable enforcement for all other tenants in the Exchange Online multitenant standard environment in March, starting with tenants with a small number of licenses, then gradually including all multitenant standard tenants by end of April.
TERRL rollout schedule
Tenant External Recipient Rate Limit is fully implemented for tenants in WW environment.
Please note that TERRL has been postponed for the following environments: GCC, GCCH, DoD, and 21Vianet. We will communicate dates for them once they have been finalized.
Based on service telemetry, most Exchange Online customers won’t be impacted. If your organization needs to send more email to external recipients than your limit allows, we recommend using dedicated high-volume email solution or purchasing additional Exchange Online licenses to cover your sending volumes.
More Information
The Tenant External Recipient Rate Limit (TERRL) is the maximum number of external recipients a tenant in good standing can send to per day (24-hour sliding window). External recipients are those whose email address domains are not an accepted domain in the tenant. The TERRL establishes base-line outbound sending limits for all tenants, but additional current and future restrictions can also occur due to factors like suspicious sending behavior, sending spam, fraudulent or excessively late payments, etc.
Below are the new maximum tenant external recipient rate limits:
- Trial tenants: Limited to 500 total external recipients per day, regardless of license count.
-
New Tenant Quotas: For newly created tenants, the calculated TERRL quota will be temporarily reduced during the initial onboarding period:
|
Tenant Age |
Applied Quota |
|
Less than 31 days |
10% of standard calculated quota (see below for standard quota calculation) |
|
31-60 days |
25% of standard calculated quota |
|
More than 60 days |
100% of standard calculated quota |
- Quota Formula for Tenants with Free EDU Licenses: For tenants that have free Education licenses (such as Microsoft 365 A1), the quota calculation will be updated to account for both purchased email licenses and free EDU licenses.
The formula is:
500 × (Purchased Email Licenses^0.7 + Free EDU Licenses^0.3) + 9500
Under this updated calculation, free EDU licenses contribute to the quota, but at a lower weight than purchased email licenses.
- Standard calculated quota for all other tenants: Daily outbound limit is based on the tenant’s email licenses (any Exchange Online or Exchange Online Protection license). More licenses increase the number of external recipients your tenant can send to per day, but at a decreasing rate per license.
500 * (Number of Non-trial Email Licenses^0.7) + 9500
Sample limits for tenants with various license counts are shown below:
|
Number of Non-trial, Non-EDU Email Licenses |
Tenant External |
|
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 |
If your tenant exceeds its daily outbound sending limit subsequent messages sent to external recipients will be blocked and senders will receive one of the following bounce messages (also known as Non-Delivery Receipts or NDRs):
- Trial tenants: 550 5.7.232 - Your message can't be sent because your trial tenant has exceeded its daily limit for sending email to external recipients (tenant external recipient rate limit)
- Non-trial tenants: 550 5.7.233 - Your message can't be sent because your tenant exceeded its daily limit for sending email to external recipients (tenant external recipient rate limit)
What is a “24-hour sliding window”?
Daily outbound email volume and quota are tracked using a 24-hour sliding window. If you exceed your limit, subsequent outbound messages will be blocked until your volume of external recipients from the last 24 hours drops below the limit. This could take minutes or up to 24 hours, depending on your email sending pattern. Here’s an example of how this works:
Example: A single-seat tenant with 10k external recipients per day limit. Tenant sends two large messages to external recipients:
- Message 1, sent to 6K external recipients at 6:00AM on Day 1
- Message 2, sent to 4K external recipients at 3:00PM on Day 1
To help admins plan and track their outbound email volume, you’ll find a new report in the Exchange admin center: EAC > Reports > Mail flow > Tenant Outbound External Recipients Rate. This report will show the current volume of external recipients, your tenant’s daily quota, how much of the quota is used, and the number of recipients that were blocked if the limit was exceeded. The report will also show if enforcement for the limit is enabled or disabled.
Sample report in EACFrequently Asked Questions
What makes a recipient an “external recipient”?
Any recipient with a domain that is not an accepted domain in your tenant is considered an external recipient and when a message is sent to them it will count against your quota (exceptions to this are noted below). This includes messages sent to recipients in other Microsoft 365 tenants.
Note: Email sent to the sub-domain won't be automatically treated as Internal. There are two conditions where we will treat email sent to subdomain as Internal:
- The subdomain is explicitly added as Accepted Domain.
- The Root accepted domain has "Accept mail for all subdomains" option enabled. Remember, this is possible only when the root accepted domain type is Internal relay.
Will journaling or Out of Office messages count against this quota?
No, journaling messages using Exchange Online journaling rules will not be counted against the quota. Several types of messages sent to external recipients from your tenant won’t get counted against your tenant’s TERRL quota, including the following:
- Journaling messages using Exchange Online journaling rules (see Manage journaling in Exchange Online | Microsoft Learn)
- Automatic Replies (including Out of Office)
- DSNs (NDRs, Delivery Receipts, Read Receipts)
- Messages sent using Azure Communication Services email and Exchange Online High-volume Email offerings
- Email notifications from Microsoft cloud applications e.g. SharePoint, Teams, Yammer
What email licenses are used to calculate my tenant’s quota?
Licenses for, or that include, Exchange Online or Exchange Online Protection count towards the license count that is used to calculate your tenant’s quota.
Are the TERRL limitations based on the total number of email licenses (Exchange Online or EOP), or the total number of assigned licenses?
TERRL is based on the total number of email licenses. For example, a tenant with 1000 licenses would be able to send 72,446 messages regardless of assigned seats (included non-licensed shared mailboxes).
Are messages to external recipients that are relayed through my tenant from my on-premises environment counted against the quota?
Yes. All messages sent outbound to external recipients from your tenant qualify for counting against your tenant’s quota, regardless of whether they originate from on-premises, from Exchange Online mailboxes, or from the Internet.
Are messages sent to my users’ on-premises mailboxes in an official Hybrid configuration counted against the quota?
So long as the mailboxes have email addresses that include an accepted domain in your tenant then these won’t count against your quota.
All my tenant’s email to internal Exchange Online mailboxes is sent out to a 3rd party service for processing before it comes back into Exchange Online to be delivered to those internal recipients. Will these messages count against my quota?
No. If the recipient’s domain is an accepted domain in your tenant messages to them won’t get counted against the tenant external recipient rate limit, even if they are routed out then back into Exchange Online.
If I send a message to an external recipient but it routes out to a signature service or on-premises for processing, then comes back into Exchange Online to be sent out to the external recipient, will that get counted twice?
We were counting these messages more than once earlier. But now we fixed this issue and email is counted only once.
Are cross-tenant messages within my multitenant organization treated as external messages?
At this time, yes.
If I send 1,000 messages to the same external recipient in a day does that count as 1 external recipient or 1,000 external recipients?
It counts as 1,000. The tenant external recipient rate limit doesn’t track unique external recipients.
If I send a message to a Distribution Group (DG) in my tenant that in turn has 1,000 external recipients on it will that get counted as 1 external recipient or 1,000 external recipients?
It counts as 1,000. The counting of external recipients happens after the DG (and its nested groups) is fully expanded to individual recipients.
Will outbound messages sent using the Exchange Online High-volume email (HVE) offering get counted against the TERRL quota?
No. HVE is designed for sending high-volume email to internal recipients, not external recipients.
How can I identify the top senders in my tenant?
You can use the “Top senders and recipients” report in the Microsoft Defender portal (Microsoft Defender > Email & collaboration reports > Top senders and recipients) or use Message Trace in the EAC to aggregate a list of your top senders. We’re also considering adding a top senders list to the Tenant Outbound External Recipient Rate report later this year.
The report shows Enforcement is Disabled. What does that mean?
When Enforcement shows Disabled blocking is not happening, even if the report shows you’ve exceeded your quota, and it shows external recipients are getting blocked. The Disabled state will be shown during the initial rollout schedule for tenants for whom enforcement hasn’t yet been enabled (see the rollout schedule above). Once the feature is fully rolled out and enabled for all tenants, Enforcement will typically always show as Enabled and blocking will occur if the quota is exceeded.
Is there any type of notification or alert I’ll get when my outbound email volume exceeds my quota?
No, not at this time. We plan to add a system alert later this year that will notify admins when their outbound email volume exceeds 80% of the quota.
Will there be a cmdlet or Graph API to retrieve the data shown in the EAC report?
You can use the below Exchange Online PowerShell cmdlet to retrieve information about your Tenant External Recipient Rate Limit:
Get-LimitsEnforcementStatus
Sample output:
Verdict : Block
EnforcementEnabled: True
Threshold: 95980
ObservedValue: 243418
|
Property |
Description |
|
Verdict |
Possible values: Block | None |
|
EnforcementEnabled |
Possible values: True | False True: Equivalent to “Enforcement is Enabled” in the report. If a tenant exceeds the TERRL the Verdict will be Block and further external messages will be blocked until the external recipient’s volume over the last 24 hours drops below the quota. False: Equivalent to “Enforcement is Disabled” in the report. Messages will not be blocked regardless of if the TERRL quota has been exceeded. |
|
Threshold |
Your tenant’s Tenant External Recipient Rate Limit (TERRL) quota based on the number of non-trial email licenses. The formula for calculating this is as follows: 500 * (number of Non-trial Email Licenses^0.7) + 9500 |
|
ObservedValue |
The number of external recipients sent to by your tenant over the last 24 hours. |
A Graph API is under consideration for a future update.
Recent changes to this blog post:
- 8/13/2026: Significant update to the post; updated limits, postponed rollout for certain cloud enmvironments etc.
- 3/26/2026: Updated GCC environment dates
- 3/19/2026: Updated the FAQ on routing to signature service or on-premises
- 2/27/2026: Updated the dates for Commercial / WW tenants
- 3/31/2025: Corrected the FAQ on "cross-tenant messages within multitenant organization"
- 3/19/2025: Clarified the status of Exchange Online journaling messages in the FAQ
Microsoft 365 Messaging Team
