How to set ispconfig so that the mails sent have the ip of the internet address IP address failover and not the address of the server ?
I don't think that it's possible. Maybe you can set that IP in the hosts file for the server for the hostname but not sure if it will cause other problems.
You don't need a failover ip to send mail. Just create mx records for each ip. You can also set an additional mx record for the failover ip with a lower value.
