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Azure Communication Services (ACS) Email – Throttling Error on Free Tier Despite Low Email Volume

Sudhanshu Shekhar 25 Reputation points
2026-04-29T05:48:48.53+00:00

We are facing unexpected throttling errors (HTTP 429) while using Azure Communication Services (ACS) Email on a Free Tier account, even though our email volume is very low.

Scenario

  • Service: Azure Communication Services – Email
  • Tier: Free Tier
  • Usage duration: More than 3 months
  • Email rate: Around 5 emails per minute
  • Emails are mostly transactional (notifications, alerts, etc.)

Issue

After using the Free Tier for over three months without any issues, ACS Email has started returning throttling errors, even when:

  • Emails are sent sequentially
  • Rate is limited to ~5 emails/minute
  • No recent increase in traffic or configuration changes

This makes email delivery unreliable, even at very low volume.

Error Observed

  • HTTP 429 – Throttling / Too many requests
  • Occurs intermittently; retry sometimes works after waiting

Questions

  1. What are the actual throttling and quota limits for ACS Email Free Tier?
  2. Is there a rolling or lifetime quota for Free Tier email usage?
  3. Does long‑term Free Tier usage trigger stricter throttling?
  4. Is this behavior expected for Free Tier accounts?
  5. Where can we monitor email-specific limits or quota consumption?

Guidance Needed

  • Should we upgrade to a paid ACS Email plan to avoid throttling?
  • Are there any recommended best practices to avoid this issue?
  • Is Microsoft recommending SendGrid or another service for production email use?

This issue is impacting application notifications and user communication, so any clarification or official guidance would be greatly appreciated.

Thanks in advance!

Azure Communication Services

Answer accepted by question author

Aditya N 2,980 Reputation points Microsoft External Staff Moderator
2026-04-29T06:53:48.83+00:00

Hello @Sudhanshu Shekhar

Thank you for reaching out Microsoft Q&A.

When you reach service limitations, you receive an HTTP status code 429 (too many requests). In general, follow these best practices for throttling:

  • Reduce the number of operations per request.
  • Reduce the frequency of calls.
  • Avoid immediate retries because all requests accrue against your usage limits

Please follow the below steps to create support request in Azure Portal.

Sign in to the Help + support - Microsoft Azure

Click on Create support request.

Enter quota in the box and click on 'Go'.

Search for Quota type: Select Service and Subscription Limits(Quotas) 

  1. Then click on Create a support request. Screenshot 2025-12-10 234101

Select Quota type as Azure Communication Services Email: Sending Limits Screenshot 2025-12-10 225920

3.Click on "Next" Screenshot 2025-12-10 231151

4.Then provide the details as the requirement. Screenshot 2025-12-10 231411

Next click on Save and Continue. You will see fields related to email sending quotas like region etc. Screenshot 2025-12-10 231913

Fill the details and Click on Review+Create.

  • Should we upgrade to a paid ACS Email plan to avoid throttling? It will be helpful
  • Are there any recommended best practices to avoid this issue? Upgradation will be helpful, based on need please select quota
  • Is Microsoft recommending SendGrid or another service for production email use? No official recommendation however ACS will be helpful.

Reference: https://learn.microsoft.com/en-us/azure/azure-portal/supportability/how-to-create-azure-support-request https://learn.microsoft.com/en-us/azure/communication-services/concepts/email/email-quota-increase https://learn.microsoft.com/en-us/azure/communication-services/concepts/service-limits#email

Kindly let us know if the above comment helps or you need further assistance on this issue.

Please "Accept" if the information helped you. This will help us and others in the community as well.Please follow the below steps to create support request in Azure Portal.

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  1. TP 156.8K Reputation points Volunteer Moderator
    2026-04-29T06:10:48.05+00:00

    Hi,

    I'm unsure what you mean by "free tier". Azure Communication Services Email is Pay-As-You-Go. Please see Messaging tab on ACS pricing page.

    If you are sending via custom domain and you haven't increased default quota, you are allowed to send up to 30 emails per minute and a maximum of 100 total emails per hour. For a managed domain the limit is up to 5 emails per minute and maximum 10 total emails per hour. You may be hitting the maximum per hour limit.

    For production use, it is intended for you to request quota increase since the default limits are too low for most cases.

    Please carefully follow my instructions below to submit quota increase request and not get stuck in endless loop. The quota increase request is free.

    Please let me know if you have any issue creating case in a comment below and I will assist further. Let me know the exact step you get stuck on and post screenshot(s) if possible.

    Please carefully follow instructions below to create a new Service and subscription limits (quotas) request to increase quota for Azure Communication Services.

    1. Navigate to this link to start the process:

    https://portal.azure.com/#create/Microsoft.Support

    2. Enter quota in the box and click Go

    User's image

    3. Select Service and Subscription Limits (Quotas) / Service and subscription limits (quotas) and click Next

    enter image description here

    4. Click Create a support request button, as shown

    User's image

    5. Select Issue type: Service and subscription limits (quotas), Subscription: <subscription that needs quota increase>, Quota type: Azure Communication Services Email: Sending Limits, click Next

    support request Problem description tab

    6. Open Notepad (or other text editor). Navigate to Email quota increase article, click Copy button in upper right to copy text, and Paste it into Notepad. Add your company info to the file and answer all questions, then save to a .txt file on your computer. You will need this file later.

    7. On Additional details tab, click Enter details, select location, resource group, ACS Email domain resource, New Email sending limit you would like to request, confirm request by entering the tier enum (200, 225, 250, 275, 300, etc.) click Save and continue.

    User's image

    enter image description here

    8. Still on Additional details tab, click the blue file folder icon, select the .txt file you created above, and click Open to upload it.

    enter image description here

    9. Finish filling out Additional details tab, click Next, review information and click Create. You should receive an automated email within a few minutes.

    Please click Accept Answer and upvote if the above was helpful.

    Thanks.

    -TP

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