What is the maximum number of emails that can be sent per minute using Microsoft Graph API

Question

What is the maximum number of emails that can be sent per minute using Microsoft Graph API, considering the limitations imposed by both Microsoft Graph API and Exchange Online?

1. Microsoft Graph API Limitations https://learn.microsoft.com/en-us/graph/throttling-limits#outlook-service-limits

A maximum of 10,000 API requests every 10 minutes.

A maximum of 4 concurrent requests.

A maximum upload of 150MB within 5 minutes.

2. Exchange Online Limit

30 messages per minute

https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits#sending-limits-1

Answer 1

Hello Aya

Thank you for reaching out to Microsoft Support!!

To determine the maximum number of emails that can be sent per minute using Microsoft Graph API, we need to account for the limitations imposed by both Microsoft Graph API and Exchange Online.

Microsoft Graph API Limitations:

• Up to 10,000 API requests per 10 minutes (averaging to 1,000 requests per minute).
• Only 4 concurrent requests are allowed at any given time.
• A maximum upload of 150MB within 5 minutes.

Exchange Online Sending Limit:

30 messages per minute is the maximum allowed.

Despite the Graph API’s high request threshold, the Exchange Online sending limit of 30 messages per minute acts as the bottleneck. Therefore, even though the API can technically handle more requests per minute, only 30 emails can be sent per minute due to the Exchange Online restriction.

Note:

• Keep in mind the concurrent request limit: If you’re designing a solution for sending emails, ensure your requests respect the 4-concurrent-request rule to avoid being throttled.
• Excessive requests breaching any of these limits will result in throttling, delays, or potential service interruptions.
• The 4-concurrent-request rule in Microsoft Graph API refers to a throttling limit that restricts the number of simultaneous requests an application can make to the API. Specifically, only 4 requests can be processed concurrently at any given time for a single app accessing a tenant. If more than 4 requests are sent simultaneously, the additional requests will be throttled, meaning they will be delayed or rejected with an HTTP status code 429 Too Many Requests.

Hope this helps.

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