question

abhilashsundaresan-2519 avatar image
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abhilashsundaresan-2519 asked MoamenHany Suspended answered

Azure -VM - SMTP inbound port 25 is blocked

Hosted Exchange server 2016 on Azure VM, and allowed Inbound Rules on port 25

( Unable to receive any emails from external )

Tested the flow from External to Azure-VM's Public IP on port 25, but its blocked

it looks Azure VM blcoked the port 25 on Public IP, The SMTP flow is already opened From Another Azure VM.

Telnet Result from External : ( Telnet PublicIP 25 : Could not open connection to the host,on port 25:Connectio failed)

Telnet result from Internal VM ( telnet servername 25) Flow is opened

Any suggestions ?

Regards,

Abhilash.

azure-virtual-machines-networking
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msrini-MSFT avatar image
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msrini-MSFT answered msrini-MSFT commented

Hi,

Outbound request to port 25 is blocked by Azure platform. For more information, take a look at this documentation.

Inbound traffic to port 25 is not blocked by platform. Can you make sure that you have allowed port 25 in the inbound rule of your NSG?


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I Yes- Outbound flow port 25- there is a known issue but not sure why inbound port 25 is blocked.
Already created Inbound Rules , All other inbound flow [ 443 /2525/587 etc] is opened except port 25

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msrini-MSFT avatar image msrini-MSFT abhilashsundaresan-2519 ·

@abhilashsundaresan-2519 , can you make sure that you allowed port 25 in the Windows Firewall?

Also on the NSG, make sure port 25 is the destination port and the source port is ANY.

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heinrich-ulbricht avatar image
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heinrich-ulbricht answered

I experience the same problem. Set up a Linux VM and cannot open INBOUND port 25.

I created inbound rules for several other ports as well - those work. Only 25 fails to work. Doing nmap on this port shows:

25/tcp closed smtp

Any help is appreciated.




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MoamenHany avatar image
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MoamenHany Suspended answered

Incoming SMTP 25 is working fine, but Outbound SMTP 25 is blocked by Microsoft Azure Article




Microsoft Azure recommended to use any 3rd Smart host or use Microsoft 365 EOP as a smart host.


http://www.moamenhany.com

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