How many emails I can send per day?

Hi @Alter Ego,

Good day, and I appreciate the clear explanation of your concern. 

The number of emails you can send per day is influenced by several factors and configurations, not just the per-recipient daily limit.

Below is a quick reference of the most common Exchange Online sending limits that may apply to your scenario. I recommend reviewing these with your IT admin to identify which threshold you may have reached:

• Per-user: 10,000 recipients/day, 500 recipients per message (configurable to 1,000), 30 messages/min
• Tenant-wide (TERRL): Formula-based cap on external recipients, with rollout phases extending into April 2026
• SMTP AUTH: 3 concurrent connections, 30 messages/min, 10,000 recipients/day
• Message size (SMTP): 25 MB
• Non-relationship recipients: 1,000/day

Even though your total send volume was 7,000 emails, you may still encounter errors such as "550 5.7.233 – Your message can't be sent because your tenant exceeded its daily limit for sending email to external recipients" due to the following common scenarios:

1/ Non-relationship recipients:

If your customers have never received an email from you before, Exchange Online classifies them as non-relationship recipients and limits you to 1,000 per day, regardless of the 10,000 overall recipient limit. It's also important to note that 1,000 is the maximum number proposed, your organization's IT admin may have configured this threshold at a lower value depending on your company's policies.

For reference: Customizable Recipient Limits in Office 365 | Microsoft Community Hub

2/ Tenant External Recipient Rate Limit (TERRL):

Daily outbound limit is based on the tenant’s email licenses (any Exchange Online or Exchange Online Protection license). More licenses increase the number of external recipients your tenant can send to per day, but at a decreasing rate per license. You’ll find your tenant’s TERRL in the Tenant Outbound External Recipients report in the EAC Reports > Mail flow section. You can also use the following formula to determine your tenant’s TERRL:

500 * (Number of Non-trial Email Licenses^0.7) + 9500

Sample limits for tenants with various license counts are shown below:

Daily outbound email volume and quota are tracked using a 24-hour sliding window. If you exceed your limit, subsequent outbound messages will be blocked until your volume of external recipients from the last 24 hours drops below the limit. This could take minutes or up to 24 hours, depending on your email sending pattern. For example:

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

Additionally, Exchange Online enforces a recipient proxy address limit of 300 and a recipient limit of approximately 200 for encrypted messages. While these limits may not directly apply to your current situation, they are worth keeping in mind for future reference.

3/ Limiting @onmicrosoft domain usage for sending emails

Microsoft enforces a throttling policy on emails sent from the default onmicrosoft.com domains. Outbound mail from these domains is limited to 100 external recipients per organization within a 24-hour rolling window. Inbound messages won't be affected. When a sender hits the throttling limit, they will receive NDRs with the code 550 5.7.236 for any attempts to send to external recipients while the tenant is throttled. External recipients are counted after the expansion of any of the original recipients. For more information, see Limiting Onmicrosoft Domain Usage for Sending Emails.

For more infomation about Exchange Online limits, please consult Exchange Online limits - Service Descriptions | Microsoft Learn

If your organization needs to send more emails to external recipients than the limits mentioned above, Microsoft recommend using Azure Communication Services email for bulk or high-volume emailing to external recipients since Exchange Online is not intended for mass or bulk email distribution. Sending 7,000 individual emails from a single mailbox falls into bulk email territory, which can:

• Trigger sending blocks and NDRs (Non-Delivery Reports)
• Negatively impact your domain's sender reputation
• Potentially flag your tenant for abuse

I hope this provides enough clarity and helps you stay inform with your current situation.

In the meantime, if you see my replies bring helpful information, please kindly accept it as an answer and vote it up by your original account, which raised this question. Once marked, it will automatically pin to top. As other users will also search information in this community, your valuable vote up will definitely also help other users who have similar queries easily to find the correct channel and useful information more quickly.   

Thank you for your patience and your understanding. If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.   

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For business mailboxes in Exchange Online (Outlook on the web for business), sending is controlled by several limits:

1. Recipient rate limit (per mailbox)
   The default policy parameter RecipientRateLimit defines how many recipients a single mailbox can send to in a 24‑hour period. An example given is 500 recipients per day for a mailbox. If the application sends to more recipients than this in a day, delivery will start failing with errors such as:
   • 5.1.90 Your message can't be sent because you've reached your daily limit for message recipients
   • 5.2.2 Submission quota exceeded
2. Message rate limit (per mailbox)
   The MessageRateLimit parameter limits how many messages can be submitted per minute. In Exchange Online this is 30 messages per minute. If the program sends faster than this, messages may be delayed (stuck in Outbox/Drafts) and delivery will be throttled.
3. Per‑recipient per‑hour limit
   There is also a limit on how many messages can be sent per hour to a specific recipient. If exceeded, error 5.2.121 Recipient's per hour message receive limit from specific sender exceeded is returned. The sender must slow down and retry later.
4. Tenant‑wide external recipient rate limit (TERRL)
   At the tenant level, there is a Tenant External Recipient Rate Limit (TERRL), which caps how many external recipients the entire tenant can send to in a 24‑hour sliding window. This depends on the number of licenses; for trial tenants it is 5,000 external recipients per day. Distribution group members are counted individually.

Because the program is trying to send to about 7,000 customers, it is very likely exceeding:

• The per‑mailbox RecipientRateLimit, and/or
• The tenant TERRL for external recipients.

To handle 7,000+ recipients:

• Use multiple days/batches so each mailbox stays under its RecipientRateLimit and the tenant stays under its TERRL; and/or
• Consider using a specialized bulk‑email solution such as Azure Communication Services email for high‑volume external mail, as recommended for scenarios that exceed Exchange Online outbound limits.

If specific limits for the tenant are needed (for example, exact TERRL value), check the Tenant Outbound External Recipients report in Exchange Admin Center → Reports → Mail flow.

References:

• Email non-delivery reports and SMTP errors in Exchange Online
• Exchange Online limits
• EWS throttling in Exchange