Vnet integration block port 25 for web app

Eugen Kasjanov 6 Reputation points
2021-07-14T15:59:23.223+00:00

Hello,

we have the problem that we can not connect to our email server on port 25 after we connect our web app to a subnet.
Without the subnet we can connect to our email server on port 25. We need the subnet for a static outbount IP.

We have a NSG witch allow in and outgoing traffic for the 25 port.

What is the issue here?

Thanks.

Azure Virtual Network
Azure Virtual Network
An Azure networking service that is used to provision private networks and optionally to connect to on-premises datacenters.
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  1. Maciej Porebski 11 Reputation points
    2021-11-02T12:39:17.367+00:00

    According to Integrate your app with an Azure virtual network - Application routing "Regional VNet integration isn't able to use port 25."

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  2. Abdul Waheed 1 Reputation point
    2021-07-14T20:47:29.123+00:00

    Vnet peering does not block any port. Only suspect could be your nsg or SMTP service itself may require some kind of white listing on new subnet.

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  3. SaiKishor-MSFT 17,176 Reputation points
    2021-07-16T23:52:53.833+00:00

    @Eugen Kasjanov Thank you for reaching out to Microsoft Q&A.

    I understand that you are unable to send outbound SMTP(port 25) traffic when you connect your web app to a subnet. This may be due tothe following:

    Outbound email messages that are sent directly to external domains (like outlook.com and gmail.com) on TCP port 25 from a virtual machine (VM) is possible only when the VM is deployed in certain subscription types. You may need to work with support to unblock this for you. Thank you!

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