Guide
Microsoft 365 email sending limits explained
Last updated July 1, 2026
If you send newsletters from Microsoft 365, Microsoft applies sending limits you need to plan around. They exist to prevent spam and protect the service, and several of them cannot be raised. Here is what matters for newsletters, with the current values from Microsoft’s documentation.
The core Microsoft 365 sending limits
| Limit | Value | Notes |
|---|---|---|
| Recipient rate limit | 10,000 recipients per day, per mailbox | 24-hour sliding window; a hard limit that cannot be increased |
| Message rate limit | 30 messages per minute | Excess is throttled and carried into following minutes |
| Recipient limit per message | 500 by default | Customizable from 1 to 1,000 by an admin |
These per-mailbox limits apply whether you send from a personal mailbox or a shared mailbox.
The tenant external recipient rate limit
Beyond per-mailbox limits, Microsoft enforces a Tenant External Recipient Rate
Limit (TERRL): the maximum number of external recipients your whole organization
can email in a day. It scales with the number of licenses in your tenant, and
trial tenants are capped at 5,000 external recipients per day. Exceeding it
returns a non-delivery report with error 550 5.7.233.
Mail to external recipients sent from a tenant’s onmicrosoft.com domain is limited to 100 external recipients per 24 hours, so always send newsletters from a custom domain.
What this means for newsletters
Microsoft’s documentation is explicit: customers who need to send legitimate bulk commercial email, such as customer newsletters, should use a service that specializes in it. That does not mean leaving your mailbox behind. SimpleNewsletter365 sends through your own Microsoft 365 mailbox over Microsoft Graph and paces delivery to stay within these limits, spreading large sends over time, so you keep your own sender identity without tripping the throttles.
Related guides
- How to send a newsletter from Microsoft 365
- How to improve newsletter deliverability on Microsoft 365
Sources
- Troubleshoot outbound sending limits for Microsoft 365 mailboxes (Microsoft Learn)
Frequently asked questions
How many emails can I send per day in Microsoft 365?
Microsoft 365 enforces a recipient rate limit of 10,000 recipients per day per mailbox, measured over a 24-hour sliding window. This is a hard limit that cannot be increased. A separate tenant external recipient rate limit also caps how many external recipients your whole organization can email per day.
What is the Microsoft 365 message rate limit?
Microsoft 365 limits each mailbox to 30 messages per minute. Messages sent faster than that are throttled and delivered over the following minutes rather than rejected.
Can I send bulk newsletters directly through Microsoft 365?
Microsoft's own documentation recommends that customers who need to send legitimate bulk email such as newsletters use a service that specializes in it. SimpleNewsletter365 sends through your mailbox while pacing within Microsoft's limits, so you stay compliant without managing the throttling yourself.
Why should I avoid sending from the onmicrosoft.com domain?
Mail sent to external recipients from a tenant's onmicrosoft.com domain is limited to 100 external recipients per 24 hours. Use a custom domain for newsletters instead.