open SMTP on Azure VM

This is blocked by design. For the rationale, exceptions, and workarounds, refer to https://video2.skills-academy.com/en-us/azure/virtual-network/troubleshoot-outbound-smtp-connectivity

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hth

Marcin

Hello Raizada, Atul,

Welcome to microsoft Q&A, thankyou for posting your query here.

Referring to the below documentation i would like to highlight some points here.

https://video2.skills-academy.com/en-us/azure/virtual-network/troubleshoot-outbound-smtp-connectivity#recommended-method-of-sending-email

There is a possibility to use port 25 for outbound communication on Azure VMs, but there are some subscription limitations as mentioned below:

For VMs that are deployed in standard Enterprise Agreement subscriptions, the outbound SMTP connections on TCP port 25 will not be blocked.

For Enterprise Dev/Test subscriptions, port 25 is blocked by default. It is possible to have this block removed.

For all other subscription types, the Azure platform will block outbound SMTP connections on TCP port 25 for deployed VMs and this block cannot be removed. This includes Pay-as-you-go.

So, when using a other than standard-enterprise subscription , users are recommended to use an authenticated SMTP relay service to send email from Azure VMs through TCP port 587, or other ports because port 25 is blocked by default and this block cannot be removed.

There are various authenticated SMTP relay services available that support port 587.

One such service is SendGrid, but there are others.

https://www.twilio.com/docs/sendgrid/for-developers/partners/microsoft-azure-2021

SendGrid accepts unencrypted and TLS connections on ports 25, 587, & 2525, and you can also connect via SSL on port 465.

Refer: https://docs.sendgrid.com/for-developers/sending-email/getting-started-smtp#send-an-smtp-email-using-telnet

Hope this helps you.

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