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Using two servers with NLB, each box contains IIS and a mail server. Server1 is the primary Server2 runs the backup mail server

The problem is the web app sends email to ourselves. When mail is sent from Server2 (via its own SMTP server) to ourselves, it tries to contact Server1, as its the mail server IP. But under Unicast mode of NLB, it cant reach the host via the public dedicated IP address.

How can we get round this?

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up vote 0 down vote accepted

Instead of trying to deliver the mail to Server 1 using the public dedicated IP address do you have a private IP that you could use? You might need to setup an entry in the hosts file on server 2 to point to the private IP.

Just a thought.

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Thanks, this is what I ended up doing just before I saw your answer. In the app code, I check if the email is bound to us, if so connect via the private IP to the primary server, otherwise send the mail via its own SMTP server. – Marcus Jan 2 '11 at 2:27

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