We are setting up a NSA 240 with dual isp connections.
Failover is set for basic active/passive failover.
Ie. one ISP fails, the other takes over within a minute.
Works great for web traffic. Nice and seamless.
But we would also like email to keep working as well.
We have an Exchange 2003 server on the inside.
Sending mail should not be a problem.
We just need to make sure that a reverse DNS entry is created at the ISP.
Its receiving it.
We have all incoming mail handled by a 3rd party anti-spam service.
Therefore the MX records are pointed at the 3rd party anti-spam service.
Once the 3rd party anti-spam service massages the email, it sends it to the Exchange server. The facility to do this, is a simple IP address entry for the applicable domain. Currently only the 1st ISP's static IP is in there. We plan to add the 2nd ISP's static ip address in there as well.
So here is the question. Is it valid to have 2 static ip addresses from different ISPs pointed at the same Exchange email server? Both technically and RFC wise?
