Microsoft 365 sending limits 2026: TERRL explained

Microsoft 365 sending limits allow each mailbox up to 10,000 recipients a day, but the cap that matters for cold email is the Tenant External Recipient Rate Limit (TERRL): a shared daily limit on external recipients for your whole tenant. A one-licence tenant gets about 10,000, and new tenants get only 10% to 25% of that at first.

Key points

• Every Exchange Online mailbox can send to 10,000 recipients in a rolling 24 hours, and 30 messages a minute.
• TERRL caps external recipients for the whole tenant, based on licence count. All mailboxes share it.
• The planned 2,000 external recipient limit per mailbox was cancelled on 6 January 2026.
• Since mid-September 2026, tenants under 31 days old get 10% of their TERRL, and 31 to 60 days get 25%. Trial tenants drop to 500.
• Hitting TERRL returns 550 5.7.233, or 550 5.7.232 on a trial tenant.

How many emails can I send per day from Microsoft 365?

You can send to up to 10,000 recipients per mailbox per day from Microsoft 365, with no more than 1,000 recipients on one message and 30 messages a minute. Your tenant's external recipients are also capped by TERRL, which is usually the lower limit for a small team sending cold email.

As of October 2026, Microsoft's Exchange Online limits page lists the same Exchange Online sending limits for every plan:

The recipient rate limit is, in Microsoft's words, "the maximum number of recipients that a user or mailbox can send to in a 24-hour period". So the Outlook daily sending limit for a Microsoft 365 mailbox is a recipient count, not a message count.

The 24 hours are a sliding window, not a calendar day. Microsoft's example: send to 5,000 recipients at 9am, 2,500 at 10am and 2,500 at 11am, and you can't send again until 9am the next day.

Microsoft is also clear about what Exchange Online is not for. The limits page says customers "who need to send legitimate bulk commercial email (for example, customer newsletters) should use third-party providers that specialize in these services", and points high-volume external mail to Azure Communication Services email.

What is TERRL?

TERRL, the Tenant External Recipient Rate Limit, is "the maximum number of external recipients a tenant can send to per day (24-hour sliding window)", according to Microsoft's limits page. External recipients are addresses whose domains aren't accepted domains in your tenant, so every cold email prospect counts.

Three details catch people out:

• It is shared. Every mailbox in the tenant draws from one pool. Ten mailboxes don't get ten caps.
• Groups are expanded. A message to a group with 1,000 external members counts as 1,000 external recipients.
• It grows slowly with licences. Microsoft's message centre post MC1454397 gives the formula for tenants without free education licences.

TERRL = 500 × (purchased email licences ^ 0.7) + 9,500

Here is the formula worked through, including the reduced quotas for new tenants described below. Figures are rounded and are our own calculations from Microsoft's formula.

Going from 10 licences to 100 doesn't even double the cap. Buying licences to send more is an expensive way to get a small increase.

You don't need to rely on the maths. Microsoft says admins can see the tenant's TERRL in the Tenant Outbound External Recipients report in the Exchange admin centre, under Reports > Mail flow. Check it before you plan any volume.

Was the 2,000 external recipient limit cancelled?

Yes. Microsoft cancelled the planned Mailbox External Recipient Rate Limit, which would have capped each mailbox at 2,000 external recipients a day. Message centre post MC787382, last updated on 6 January 2026, says Microsoft "decided not to proceed with the rollout of this limit".

MC787382 was first published on 26 April 2024. It planned to "enforce a 2,000 external recipient rate limit within the existing 10,000 recipient limit", starting with new and trial tenants. Many older guides still quote the 2,000 figure, so be wary of anything that hasn't been updated since.

That leaves two limits: 10,000 recipients per mailbox and TERRL per tenant. Treat both as ceilings, not targets. Sending anywhere near them from one mailbox will damage your domain's reputation long before Microsoft stops you.

What do 550 5.7.232 and 5.7.233 mean?

550 5.7.233 means your tenant has hit its TERRL, and 550 5.7.232 means a trial tenant has hit its trial external recipient limit. Both are bounces from your own Microsoft 365 tenant, not rejections by the recipient's server.

According to MC1454397, once the limit is reached, further messages to external recipients are blocked until usage drops back under the limit in the rolling 24-hour window.

A related code: 550 5.7.236 means you've sent from the default onmicrosoft.com domain past its cap. The limits page says that domain is limited to "100 external recipients per organization within a 24-hour rolling window". Add and verify your own domain before you send anything.

If your bounces instead show codes like 550 5.7.26 or 5.7.515, the recipient's provider rejected you for authentication. Our guide to email sender requirements in 2026 covers those.

What changed for new and trial tenants?

Since mid-September 2026, new tenants get a reduced TERRL for their first 60 days, and trial tenants drop to 500 external recipients a day. Microsoft announced this in MC1454397 and expects the rollout to finish by the end of November 2026.

MC1454397 was published on 14 August 2026 and updated on 29 September 2026. For new tenants, the quota depends on age:

• Less than 31 days old: 10% of the standard calculated quota.
• 31 to 60 days old: 25%.
• More than 60 days old: 100%.

So a new tenant with 10 licences gets roughly 1,201 external recipients a day in its first month and roughly 3,001 in its second, instead of 12,006.

For trial tenants, the post says the daily quota drops from 5,000 to 500 external recipients. Sources differ here: Microsoft's Exchange Online limits page, updated 19 October 2026, still says the trial limit "is capped at 5,000 external recipients per day". The rollout runs until the end of November 2026, so assume the lower figure and check your Mail flow report.

Education tenants with free licences, such as A1, move to a new formula in which free licences count for less. Microsoft says the aim is to "strengthen protection against abuse and ensure fair use of Exchange Online resources". The practical lesson: a freshly bought tenant is the worst place to start sending cold email.

How do you plan cold email around Microsoft 365 sending limits?

Plan cold email well below Microsoft 365 sending limits, because the real risk is reputation, not the cap. A sensible plan:

1. Send from your own domain, with SPF, DKIM and DMARC set up before the first email. Never from onmicrosoft.com.
2. Keep daily volume per mailbox small. A few dozen cold emails a day per mailbox is far below Microsoft's limits and much safer than hundreds.
3. Spread sending across a few mailboxes, remembering they all share one TERRL.
4. Start slowly. Begin new mailboxes at a handful of emails a day and build up over weeks. On a new tenant, the 10% and 25% quotas enforce this for you.
5. Keep a buffer. Plan your daily total well under your TERRL, so replies and normal business mail never get blocked.
6. Treat 5.7.232 or 5.7.233 bounces as a stop sign, then check the Mail flow report.

A bad plan: buy a new tenant on Monday with one licence and try to send 2,000 cold emails from one mailbox on Tuesday. That tenant gets about 1,000 external recipients a day for its first month, so half the run bounces, and the rest comes from a mailbox with no history.

A good plan: three mailboxes on a dedicated domain with SPF, DKIM and DMARC, each starting at 5 to 10 emails a day and rising gradually, with the total well under the tenant's cap.

Where Outbind fits

Outbind sends from your own Gmail or Outlook mailboxes, so these Microsoft limits apply to you as they would to anyone. It sends up to 50 emails a day per mailbox, starts new mailboxes slowly, rotates sending across the mailboxes you connect and only sends between 8am and 8pm in the recipient's time zone. That keeps a small team far below TERRL. Every plan has a 7-day free trial; see pricing.

FAQ

What is the Microsoft 365 daily sending limit?

Each mailbox can send to 10,000 recipients in a rolling 24 hours, with up to 1,000 recipients per message and 30 messages a minute. External recipients across the whole tenant are also capped by TERRL.

How is TERRL calculated?

For tenants without free education licences, Microsoft's formula is 500 × (purchased email licences ^ 0.7) + 9,500. One licence gives 10,000 external recipients a day, and 100 licences give about 22,059.

Is there still a 2,000 external recipient limit per mailbox?

No. Microsoft cancelled the planned 2,000 per-mailbox external limit, according to MC787382 as updated on 6 January 2026.

What does 550 5.7.233 mean?

It means your tenant has reached its Tenant External Recipient Rate Limit. Mail to external recipients is blocked until your usage in the rolling 24 hours drops below the limit.

How much can a new Microsoft 365 tenant send?

Under MC1454397, a tenant less than 31 days old gets 10% of its standard TERRL and a tenant 31 to 60 days old gets 25%. For a one-licence tenant, that's about 1,000 and 2,500 external recipients a day.

Sources

• Microsoft Learn: Exchange Online limits
• Microsoft 365 Message Center MC1454397 (via merill.net): Updates to Tenant External Recipient Rate Limit (TERRL) Quotas for New, Trial, and Education Tenants
• Microsoft 365 Message Center MC787382 (via merill.net): Exchange Online to introduce External Recipient Rate Limit