Yes, bydefault these ports are blocked for both new and existing customers to prevent malicious users from using Azure IP addresses
for abuse and adversely affecting the reputation of all Azure IPs.
Microsoft recommends that you utilize authenticated SMTP relay services (typically connected via TCP port 587, but often others, as
well) to send email from Azure Virtual Machines. SMTP relay services specialize in sender reputation, to minimize the possibility that third-party email providers reject messages. Such SMTP relay services include, but are not limited to, Exchange Online Protection
and SendGrid. Use of SMTP relay services is in no way restricted in Azure, regardless of your subscription type.
- Pay-as-you-go: Outbound port 25 communication
is blocked from all resources. If you need to send email from a virtual machine directly to external email providers (not using an authenticated SMTP relay), you can make a request to remove the restriction. Requests are reviewed and approved at Microsoft's
discretion and are only granted after anti-fraud checks are performed. To make a request, open a support case with the issue type Technical, Virtual Network Connectivity, cannot send e-mail (SMTP/Port 25).
Suggest you to refer the below article:
https://docs.microsoft.com/en-us/azure/virtual-network/security-overview#azure-platform-considerations
NOTE: If Azure allows you to send email over port 25, Microsoft cannot guarantee email providers will accept inbound email
from your virtual machine. If a specific provider rejects mail from your virtual machine, you must work directly with the provider to resolve any message delivery or spam filtering issues or use an authenticated SMTP relay service.
Also, would suggest you to upvote in the
feedback link regarding the blocked ports.
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