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Outbound email not sending from cPanel/WHM server hosted on Azure

Balasubramanian Rajendran 0 Reputation points
2026-03-09T11:19:16.72+00:00

Hello Azure Support,

I am experiencing an issue with outbound email from my server hosted on Azure.

My setup is:

  • Domain DNS is managed at Hostinger

Website and email are hosted on a cPanel/WHM server running in Azure

Problem:

My email accounts are unable to send outgoing email

Incoming mail may be working, but outbound sending is failing

This appears to be affecting the mail service running on my cPanel/WHM server

I need your help checking whether Azure is blocking or restricting SMTP traffic from my VM/server.

Please verify:

Whether outbound SMTP ports are blocked or restricted on my Azure VM/subscription

Whether there are any networking, NSG, firewall, or platform-level restrictions affecting mail delivery

Whether my public IP or VM has any outbound email limitations or reputation-related restrictions

Whether port 25, 465, or 587 outbound traffic is allowed from my server

Whether I need an SMTP unblocking request or any additional configuration from Azure side

Server details:

Hosting platform: Azure VM

Control panel: cPanel/WHM

Domain DNS: Hostinger

Mail service: cPanel/Exim

Issue details:

Outbound emails are not being sent successfully

Please let me know if Azure can see blocked SMTP attempts or any related network restriction

Please advise what checks I should perform on the server side as well, and let me know if you need my VM name, subscription ID, public IP, or error logs.

Thank you.Hello Azure Support,

I am experiencing an issue with outbound email from my server hosted on Azure.

My setup is:

Domain DNS is managed at Hostinger

Website and email are hosted on a cPanel/WHM server running in Azure

Problem:

My email accounts are unable to send outgoing email

Incoming mail may be working, but outbound sending is failing

This appears to be affecting the mail service running on my cPanel/WHM server

I need your help checking whether Azure is blocking or restricting SMTP traffic from my VM/server.

Please verify:

Whether outbound SMTP ports are blocked or restricted on my Azure VM/subscription

Whether there are any networking, NSG, firewall, or platform-level restrictions affecting mail delivery

Whether my public IP or VM has any outbound email limitations or reputation-related restrictions

Whether port 25, 465, or 587 outbound traffic is allowed from my server

Whether I need an SMTP unblocking request or any additional configuration from Azure side

Server details:

Hosting platform: Azure VM

Control panel: cPanel/WHM

Domain DNS: Hostinger

Mail service: cPanel/Exim

Issue details:

Outbound emails are not being sent successfully

Please let me know if Azure can see blocked SMTP attempts or any related network restriction

Please advise what checks I should perform on the server side as well, and let me know if you need my VM name, subscription ID, public IP, or error logs.

Thank you.

Azure Firewall
Azure Firewall

An Azure network security service that is used to protect Azure Virtual Network resources.

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  1. Thanmayi Godithi 8,310 Reputation points Microsoft External Staff Moderator
    2026-03-09T16:13:10.94+00:00

    Hi @Balasubramanian Rajendran,

    Thank you for reaching out on Microsoft Q&A forum.

    Azure applies platform‑level restrictions on outbound SMTP over TCP port 25 for most subscription types to prevent spam. This block is enforced outside the VM, so NSGs, UDRs, OS firewall rules, or cPanel settings cannot override it. As a result, inbound email can work while outbound delivery fails or times out.
    Microsoft documentation:

    Subscription behavior (important)

    • Enterprise Agreement (EA) / MCA‑E (standard): Outbound SMTP on port 25 is not blocked by Azure, but delivery to external domains is not guaranteed (remote providers may still reject based on IP reputation).
    • Enterprise Dev/Test: Port 25 is blocked by default; you can request removal via Virtual Network → Diagnose and Solve → “Cannot send email (SMTP‑Port 25)”, then stop, deallocate, and start the VM for the policy to apply.
    • All other subscription types (PAYG, Student, etc.): Port 25 is blocked and cannot be used.

    Microsoft recommends using an authenticated SMTP relay instead of direct SMTP on port 25. Authenticated relays use TCP port 587 (or 465), which is not blocked in Azure for any subscription type, and provides better deliverability and IP reputation management.

    Kindly share the details requested over Priavate message if you need further assistance on this issue!

    If the answer is helpful, please "Accept the answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

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