Hi everybody, I'd like to know if it's possible to setup Exchange 2003/2007 to switch between smarthosts, based on the WAN connection currently in use. Example scenario: I have two WAN connections with different ISP's. Exchange is running behind a dual WAN router. The router is setup to fall back to secondary WAN when primary WAN fails. The smarthost set in Exchange is the SMTP server of the primary ISP. Because the smarthost set in Exchange only allows relaying from IP's of the primary WAN sending mail won't work when the router falls back to the secondary WAN. Sending mail directly through DNS MX lookup is an option but the ISP's have dynamic IP's that get blacklisted a lot. Thanks in advance!