Using Exchange 2003 in SBS2003 R2. We've setup a router with dual-wan capability in a fail-over mode (if wan1 goes down, wan2 opens up). We've setup the 2 mx records to point to the 2 public addresses and can receive email fine on wan2 when wan1 goes down.
Our problem is with sending. Our Exchange is configured to send mail through ISP1 smarthost, say smtp.isp1.net. When wan1 goes down, outgoing mail will go through wan2, but ISP2 will refuse to relay mail that is going to smtp.isp1.net, which is normal.
So how do you setup Exchange to use smtp.isp2.net smarthost when the "regular" Smtp connector using smtp.isp1.net does not work ?