Azure Migrated Server - SMTP Traffic Bypassing NAT Gateway

abeer hayat khan 0 Reputation points
2024-04-08T03:59:45.9866667+00:00

I have migrated an on-prem server to the Azure cloud.

Machine Details: Name: Horizon Private IP: 192.168.1.10 Subnet: Development NAT Gateway: azure-nat Public IP on NAT: 104.233.121.78

When surfing the web, the public IP check returns source IP as 104.233.121.78. When sending SMTP traffic to EOL Relay the Source address in the local SMTP logs is 513.95.218.52.  It seems that the SMTP (or custom TCP/UDP Port 25) traffic is not adhering to the Nat Gateway when it should.

Can you advise why the SMTP traffic is originating from the Random MS Cloud address and not the NAT Gateway IP Address 104.233.121.78?

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.
2,427 questions
Azure NAT Gateway
Azure NAT Gateway
NAT Gateway is a fully managed service that securely routes internet traffic from a private virtual network with enterprise-grade performance and low latency.
35 questions
0 comments No comments
{count} votes

1 answer

Sort by: Most helpful
  1. KapilAnanth-MSFT 45,111 Reputation points Microsoft Employee
    2024-04-08T06:28:13.39+00:00

    @abeer hayat khan ,

    Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.

    • May I ask how you are confirming 513.95.218.52 is a "Random MS Cloud address" ?
    • In fact, "513.95.218.52" is not even a valid IP Address, as we know IPV4 can only range between 0.0.0.0 to 255.255.255.255.
    • Moreover, it appears the IP which you have shared as NAT Gateway IP Address, "104.233.121.78" belongs to a 3rd party ISP and not Azure.
      Can you share a screenshot of the Public IP from the Azure Portal, like below?
      User's image

    I would suggest you to please double-check your logs and give us more information as to what the exact issue is.

    Cheers,

    Kapil


Your answer

Answers can be marked as Accepted Answers by the question author, which helps users to know the answer solved the author's problem.