Unable to send email

Administrator admin 0 Reputation points
2026-11-02T23:32:36.04+00:00

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

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Exchange | Other

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  1. Dora-T 1,990 Reputation points Independent Advisor
    2026-11-03T00:30:21.6866667+00:00

    Hi @Administrator admin

    Based on the error message provided, the issue appears to be related to the Tenant External Recipient Rate Limit (TERRL) in Exchange Online.

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    I would recommend reviewing the AI-generated answer, as it contains detailed guidance on this scenario. 

    If the tenant has reached its external recipient limit, outbound messages to external recipients may be temporarily blocked until the recipient count falls back below the allowed threshold. In most cases, the recommended action is to pause external email traffic and wait for the rolling 24-hour window to expire before attempting to send externally again. 

    A Microsoft 365 administrator may also review the Tenant Outbound External Recipients report in the Exchange admin center > Reports > Mail flow > Tenant Outbound External Recipients Rate to verify the tenant's current external recipient usage. 

    For reference: Introducing Exchange Online Tenant Outbound Email Limits | Microsoft Community Hub 

    Additionally, if outbound email is being sent from the default onmicrosoft.com domain, you may find the following article helpful, as it explains the separate sending limits that apply to that domain: Limiting Onmicrosoft Domain Usage for Sending Emails | Microsoft Community Hub   

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  2. AI answer

    2026-11-02T23:33:12.4433333+00:00

    Stop sending to external recipients and wait until your tenant’s external-recipient count for the rolling 24-hour window falls below its Tenant External Recipient Rate Limit (TERRL); Exchange Online will then automatically allow external sending again.^1^

    Check the tenant’s current usage

    A Microsoft 365 or Exchange administrator should:

    1. Open the Exchange admin center.
    2. Go to Reports → Mail flow.
    3. Open Tenant Outbound External Recipients.
    4. Review the current usage and the TERRL assigned to the tenant.

    TERRL is tenant-wide and scales automatically with the number of licenses. A trial tenant is capped at 5,000 external recipients per day. Distribution-list members are counted individually after the list and any nested groups are expanded.^2^

    While the limit is exceeded:

    • External messages from all users in the tenant are rejected with 550 5.7.233.
    • Internal mail is not identified by this error as blocked.
    • Retrying repeatedly does not reset the limit; sending resumes only as older recipients leave the rolling 24-hour calculation.^3^

    Prevent it from recurring

    • Pause scheduled jobs, applications, mail merges, and campaigns that send externally.
    • Identify the largest senders using message trace and mail-flow reports.
    • Stagger normal external communications rather than sending them in one batch.
    • Remember that sending one message to a group containing 1,000 external members counts as 1,000 external recipients.
    • For bulk or high-volume external email, move the workload to Azure Communication Services Email or another dedicated bulk-email provider. Exchange Online is not designed for bulk-mailing scenarios.^3^

    If the NDR is 550 5.7.236

    This is a different limit applying to mail sent from the tenant’s default onmicrosoft.com domain. That domain is limited to 100 external recipients per tenant in a rolling 24-hour period and is intended for testing rather than regular outbound mail.

    In that case:

    1. Add and configure a custom domain in Microsoft 365.
    2. Assign users addresses on that domain.
    3. Send external mail only from the custom domain.
    4. Wait for the existing onmicrosoft.com recipient count to fall below its rolling-window limit.^1^

    If the report shows that usage is already below the applicable limit but the same NDR continues, open a Microsoft 365 support request and include the complete NDR, timestamps, affected senders, and a screenshot or export of the Tenant Outbound External Recipients report.

    References

    1. Email nondelivery reports and SMTP errors in Exchange Online
    2. Exchange Online limits
    3. Troubleshoot outbound sending limits and blocked users in Exchange Online
    AI-generated content may be incorrect. Read our transparency notes for more information.

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