Request for Assistance with Azure Communication Services – Email Configuration and SMTP Access

Question

Hello Azure Support Team,

I hope you are doing well.

We are currently using an Azure Virtual Machine to host our services. Incoming email is working correctly; however, outgoing email from the VM is not working. After reviewing the mail server logs, we confirmed that outbound SMTP connections to external mail servers (such as Gmail) are timing out, which indicates Azure outbound SMTP restrictions.

To resolve this in a supported and compliant manner, we would like to use Azure Communication Services – Email for all outgoing emails.

We kindly request your assistance with the following:

Confirmation and guidance on using Azure Communication Services – Email as the official solution for outgoing emails from Azure VMs.

1. Assistance in ensuring that SMTP access (Port 587 with STARTTLS) for Azure Communication Services – Email is properly enabled and usable from our VM.

Any recommended best practices or required configurations (network, firewall, or subscription-level) to ensure reliable outgoing email delivery using Azure Communication Services – Email.

Confirmation that no additional outbound SMTP restrictions will affect email delivery when using Azure Communication Services – Email.

Answer 1

Hi @subahm Puri
Azure Azure Communication Services Email is the official Microsoft-recommended solution for sending outbound emails from Azure resources like Azure Virtual Machine. This is because Azure blocks direct outbound SMTP connections to external email providers (such as Gmail) by default to prevent spam and abuse, and these restrictions cannot be lifted for consumer email services. Azure Communication Services Email addresses this limitation by letting applications on Azure send emails in a supported way, without needing unrestricted SMTP access.

It mainly uses secure HTTPS-based REST APIs to send emails, which are not affected by Azure’s SMTP blocking. Using the API-based method means no extra SMTP restrictions apply, and email delivery from Azure VMs remains reliable. While authenticated SMTP submission on port 587 with STARTTLS is available (if enabled), Microsoft still recommends using REST APIs for better reliability and monitoring, as they avoid port-level restrictions.

For successful email delivery, Microsoft suggests verifying the sender domain with necessary DNS records (SPF, DKIM, and DMARC), allowing outbound HTTPS traffic (port 443) from the VM, and monitoring email delivery using Azure Communication Services logs and Azure Monitor. Following these practices ensures that Azure Communication Services Email works well within Azure’s SMTP restrictions and is fully supported for production use.
https://learn.microsoft.com/en-us/azure/communication-services/concepts/email/email-overview
https://learn.microsoft.com/en-us/azure/communication-services/quickstarts/email/send-email?tabs=windows%2Cconnection-string%2Csend-email-and-get-status-async%2Casync-client&pivots=platform-azportal
https://learn.microsoft.com/en-us/azure/virtual-network/troubleshoot-outbound-smtp-connectivity
Let me know if you have any further assistances needed.

Answer 2

To use Azure Communication Services – Email for outgoing emails from your Azure Virtual Machine (VM), you can follow these guidelines:

1. SMTP Access: Azure Communication Services – Email uses authenticated SMTP relay services, typically connecting via TCP port 587. This port is not blocked in Azure, making it a reliable option for sending emails. Port 25 is generally restricted for outbound SMTP connections from Azure VMs, so using port 587 is recommended.
2. Configuration: Ensure that your Azure VM is configured to connect to Azure Communication Services using the appropriate SMTP settings. You will need to authenticate using the credentials provided by Azure Communication Services.
3. Best Practices:
   • Utilize authenticated SMTP relay services to maintain a good sender reputation, which helps in ensuring that your emails are delivered reliably.
   • Monitor the rate limits set by Azure Communication Services to ensure they meet your application's needs. If necessary, you can open a support case to request an increase in these limits.
   • Ensure that your network security groups and firewall settings allow outbound connections to the SMTP relay service.
4. No Additional Restrictions: When using Azure Communication Services – Email, there are no additional outbound SMTP restrictions that will affect your email delivery, as it operates independently of the restrictions applied to direct SMTP connections from Azure VMs.

By following these guidelines, you should be able to configure your Azure VM to send outgoing emails effectively using Azure Communication Services – Email.

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References:

• Troubleshoot outbound SMTP connectivity problems in Azure
• Help and support options for Azure Communication Services