TERRL Exchange error message

Question

TERRL Exchange error message

icon 814wraps 0

This started happening yesterday without warning. Fron what I've read, it's about sending too many emails in a single day. I'm not sure what that number is but we've only sent about 15-20 emails in the last two days. How do I stop this so I can email my clients?

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). For more information see https://aka.ms/EXONdrs.'

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2 answers

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Answer 1

Anonymous

Hi @icon 814wraps,

Thank you for sharing the error message.

To clarify, the NDR you’re seeing (550 5.7.233) is generated by Exchange Online’s Tenant External Recipient Rate Limit (TERRL). This is a tenant‑wide protection limit, meaning it applies to the entire organization and not just to your individual mailbox.

Based on my review, the reason you’re currently unable to send emails is that this TERRL limit has been exceeded. In simple terms, TERRL defines the maximum number of external recipients that a tenant in good standing can send emails to within a 24‑hour sliding window.

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Once this limit is reached, the block is applied immediately. However, it is also lifted automatically as soon as the sending volume drops below the threshold within that same 24‑hour window. At this point, the only required action is to wait until the 24‑hour period has passed and the limit resets.

For more detailed information about TERRL and how the 24‑hour sliding window works, you can refer to this article: Introducing Exchange Online Tenant Outbound Email Limits | Microsoft Community Hub

I hope this explanation helps clarify the situation. If I’ve misunderstood anything or if you feel this doesn’t fully match what you’re experiencing, please let me know and I’ll be happy to work through it with you.

Thank you for your patience and understanding. I look forward to your reply.

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icon 814wraps 0 Reputation points

2026-03-12T18:34:43.6366667+00:00

I understand. I guess I'm trying to figure out why it would be happening to us and what the email limit would be. We are a small company with one email address and only three computers. We email customers back and forth a little but in no way send more than maybe 20-30 emails a day and that would be on the high end.
Anonymous

2026-03-12T18:50:36.37+00:00
Hi @icon 814wraps,

Thank you for your response, your question in completely understandable.

What makes this situation confusing is that TERRL is not based on the number of emails you send, but rather on the total number of external recipients your tenant sends to within a rolling 24‑hour window. Microsoft doesn’t publish the exact numeric threshold, and it can vary depending on tenant reputation and activity patterns.

Because of that, even a small company can unexpectedly hit this limit if, for example:

Emails are sent to multiple external recipients at once (including CC or BCC),

Messages are forwarded externally,

There are automatic replies, signatures, or notifications going to external addresses,

A device, app, or mailbox is sending mail in the background without being obvious,

Or there was a short spike in activity within the last 24 hours, even if overall volume feels low.

This is also why it can appear to happen without warning, especially when usage patterns change slightly or when Microsoft’s protection systems detect behavior that temporarily exceeds normal thresholds.

Unfortunately, there is no way to manually remove or override this block. Once triggered, it is enforced automatically and will clear on its own as soon as the external recipient volume drops below the limit within the 24‑hour sliding window.

At this point, the next steps you could do are:

Allow some time for the 24‑hour window to roll forward,

Avoid sending messages to multiple external recipients at once during that period,

Review whether any shared mailboxes, devices, or apps might also be sending external mail under your tenant.

I completely understand how disruptive this is, especially for a small business communicating with clients. If the issue continues after the window has passed, please let me know and we can look more closely at possible hidden senders or escalation options.

Thank you again for your patience. I’m here to help if you need further assistance.
Anonymous

2026-03-13T22:23:21.4+00:00

Hi @icon 814wraps,

I hope everything is going well on your end.

I am following up on the support thread that has been discussed and wanted to check whether the information shared in my previous response helped address the issue you were experiencing.

If you are still encountering any issues or have additional questions, please feel free to reach out at any time. I would be happy to assist further as needed.

Additionally, ensuring that everything is functioning as expected and that your experience remains smooth is a top priority.

Thank you again for your collaboration throughout the troubleshooting process. I look forward to hearing from you soon.

Warm regards,

Answer 2

Error code 550 5.7.233 indicates that the tenant has exceeded the Tenant External Recipient Rate Limit (TERRL) for Exchange Online.

Key points from the error and limits:

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)."
TERRL is the maximum number of external recipients (domains not configured as accepted domains in the tenant) that can be sent to in a rolling 24‑hour window.
The limit is per tenant, not per mailbox, and depends on the number of licenses in the tenant.
Distribution group members are counted individually after expansion. For example, sending one email to a group with 1,000 external members counts as 1,000 external recipients.

Why this can happen even if only 15–20 emails were sent:

Another mailbox or application in the tenant may be sending to many external recipients.
Messages to large distribution lists with external members can quickly consume the limit.
The count is per recipient, not per message.

How to restore sending:

TERRL is enforced over a 24‑hour rolling window. When the total external recipients sent to in the most recent 24 hours falls back below the tenant’s limit, sending to external recipients will automatically resume.
Until then, messages to internal recipients (within accepted domains) should still work; only external recipients are blocked.

What an admin should do:

In the Exchange admin center (EAC), go to Reports → Mail flow → Tenant Outbound External Recipients to see:
- The tenant’s current TERRL value.
- Which senders are consuming the external recipient count.
Check for:
- Compromised accounts or apps sending bulk mail.
- Workflows, CRM systems, or automated mailers sending to many external recipients.
Reduce external recipient volume:
- Use distribution groups or Microsoft 365 groups where appropriate, but be aware that external members are still counted individually.
- Stagger large sends over multiple days so the 24‑hour rolling total stays under the limit.
- For sustained bulk or high‑volume external mail, move that workload to a service designed for it, such as Azure Communication Services email.

Once the 24‑hour external recipient count drops below the tenant’s TERRL, normal external sending will resume automatically; no manual unblocking is required if there are no other issues.

References: