Quoting Grant Peel:
> helo_data = ${lookup
> dnsdb{defer_never,ptr=$interface_address}{$value}{$primary_hostname}}
> interface = $interface_address
So the interface address the mail was delivered through will be used for
the outgoing connection? Looks clever to me, almost too clever... I'm
not sure if I would use it. But I guess it will work.
And as I pointed out, just make sure that none of your customers abuse
your system by sending mail through the interface address of another
customer, ACLs are good for that.