Publish an SMTP server on TMG2010

Hello Experts,

I am trying to publish an Exchange 2007 SMTP server listening on port 25 to the WEB behind two firewall zones and TMG.

Security design is the following :
[ WEB ] -- [ FW VLAN 6 ] -- [ TMG ] -- [ FW VLAN 10 ] -- [ EXCHANGE VLAN 1 ]

On TMG, i have set 2 network interfaces :
- VLAN06 with IP as a perimeter interface
- VLAN10 with IP as an internal interface

Some tests :
- SMTP trafic is forwarded from public IP to VLAN06 to TMG (rule approved it and log trace)
- Inbound trafic is received on TMG (log trace)
- No trafic logged from TMG to Exchange
- I am able to telnet Exchange on port 25 from TMG

My problem :
Running a telnet from outside to my pub address on port 25, i am not connected.

I get an error : no rule seems to autorize my demand.
Source : perimeter network with remote public address
Destination : local host with VLAN06 address

Rule is set to autorize SMTP from localhost / perimeter to Exchange

Sometimes, I can get an WSAECONNREFUSED error without changing anything in the rule set.

Any help would be great.
Best regards,
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Amit BhatnagarTechnology Consultant - SecurityCommented:
Did you say 'Rule' on TMG? This is an incorrect way of allowing the traffic from Perimeter Network to Internal.
What Network relationship is present between Perimeter Network and Internal? Is it NAT or Route?
Ideally, It should be External and Internal Network on TMG because what is Perimeter to your External Firewall is actually "External" to TMG.
Now, you need to create a Mail Server Publishing Rule on your TMG and NOT a firewall rule. If you do not want to change the configuration of TMG i.e. Convert Perimeter to External then make sure, once the Mail Server Publishing Rule has been created, you go into the properties of the rule then Networks and make it listen on Perimeter Network and NOT External cause we do not have any External..:)

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