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New Member

PIX+Microsoft IIS SMTP

I have 2 mail servers running Imail on my network. Now i have got a customised application of my client to run on my network. My network is equpiied with cscpo pix 525 with IOS 6.1 .

The application sends mail from the IIS virtual SMTP server which directly relays tyhe m,ails to the domains. I get these mails to the outside domains like yahoo, hotmail etc. But im not getting the mails to domains inside the firewall.I send mails to my ID and it gets delivered. I send mail to , it will not get delivered. All my mails are confugured as follows:

eg: is my domain. I have pointed the mail to which is inside my firewall.the respective alias entries also have been given in the firewall for this. when i ping its pinging the internal IP.

is there anything which i need to do in the firewall or IIS SMTP for this to get solved.

can anyone help me out on this ?

thanks in advance.



Re: PIX+Microsoft IIS SMTP

I assume that the MX record for is pointing to And when you ping it is resolved to an internal IP adres?

If that is true then the traffic is not going through the pix and is the problem related to you IIS smtp server.

Does the IIS SMTP server deliver the mail directly to the destination, or does it forward it's traffic to a 'forwarding' mail server that will take care of the delivery? If you use a 'forwarding' mail server of your provider to deliver the mail, that mail servers probabely does not know how to deliver mail to your

If you still think that the pix is causing the problems, maybe you could enable syslog logging on the pix:

logging host inside

logging trap debug

logging on

(free syslog server at

Kind Regards,


New Member

Re: PIX+Microsoft IIS SMTP

the IIS is directly delivering the mails. Its not using any other server for this relay.


Re: PIX+Microsoft IIS SMTP


does the syslog messages from the pix show that the pix is blocking something?

Maybe you could sniff the traffic coming from your mailserver, that way you are sure that the mail server is actually sending the smtp data.

In case you don't have a sniffer yet:

Best Wishes,