We have our main external IP range lets call it 22.214.171.124 for our T1 line, and firewall, and exchange server etc. The firewall has been configured for failover, so that it the T1 goes down, the DSL will kick in - it's IP's are 126.96.36.199
On the external MX records, I can send the email to the 188.8.131.52 IP's if the 184.108.40.206 is down. The iphone has an A record called iphone.myco.com which points to the IP of the mail server - say 66.66.66.01and it works fine. When the failover happens, the iphone will not get email because it is not pointing to the 44.44.44.01 (the DSL's IP for the exchange server)
Can I set up the MX records or the iphone itself so that the failover will allow the iphone to continue to get email automatically when the T1 is down?