Request to unblock outbound port 25 (SMTP) - On-premises migration to Azure

Hi Craftech,

Thanks for reaching out in Microsoft Q&A forum,

Based on the information shared, the ability to send outbound SMTP traffic over port 25 from Azure depends on the subscription type associated with your environment. This restriction is enforced at the Azure platform level and cannot be modified through Network Security Groups (NSGs), User Defined Routes (UDRs), or operating system firewall settings.

For Enterprise Agreement (EA) and Microsoft Customer Agreement for Enterprise (MCA-E) subscriptions, outbound port 25 is generally permitted by default. For Enterprise Dev/Test subscriptions, an exemption may be requested through the Azure portal by navigating to the Virtual Network resource and running the Cannot send email (SMTP-Port 25) diagnostic under Diagnose and solve problems. If approved, a restart of the virtual machine may be required for the change to take effect.

For Pay-As-You-Go (PAYG), Free Trial, CSP, and other non-enterprise subscription types, outbound port 25 is restricted by Azure policy and is not eligible for exemption.

Given that your application currently relies on port 25 and does not support STARTTLS or alternative SMTP ports such as 587 or 465, we recommend first confirming the subscription type of the target Azure environment. This will help determine whether outbound SMTP on port 25 is supported or whether an alternative email delivery architecture will be required.

For additional information, please refer to the following Microsoft documentation:

Troubleshoot Outbound SMTP Connectivity in Azure - Azure | Microsoft Learn

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

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