Email Sending Limits in Microsoft 365
Microsoft 365 enforces specific email sending limits to ensure service integrity and prevent abuse such as spam or unauthorized bulk messaging. These limits vary depending on your subscription plan.
1. Daily Sending Limit
This is the maximum number of recipients a single account can reach within a 24-hour period:
- Microsoft 365 Business Standard/Premium and Enterprise (E1, E3, E5): 10,000 recipients per day
- Microsoft 365 Business Basic: 10,000 recipients per day
- Exchange Online Kiosk: 300 recipients per day
2. Per-Message Recipient Limit
Each email can be sent to a maximum of 500 recipients at once, including To, Cc, and Bcc.
3. Sending Rate Limits
Microsoft controls sending speed and simultaneous SMTP connections to avoid overload:
- When using an authenticated SMTP relay: up to 30 messages per minute
- Up to 10,000 recipients per day per account
Temporary Sending Block
If an account exceeds the defined limits, email sending will be blocked for 24 hours. During this time, the user will not be able to send new messages but can still receive emails.
Monitoring and Management
You can track your email usage and receive alerts through the Microsoft 365 Security & Compliance Center or by using third-party tenant management tools.
Recommendations for Bulk Email
For marketing campaigns or large-scale email sending, consider using professional tools such as:
- Microsoft Dynamics 365 Marketing
- Third-party platforms (e.g., Mailchimp, SendGrid)
These solutions provide better deliverability, analytics, and compliance with anti-spam regulations.
Need help?
Contact us for support or more information about managing email sending in Microsoft 365.
