Outgoing SMTP Traffic from AntiSpam Appliance

Dear HAProxy Community,

we have the following problem: I am using an AntiSpam Mail Appliance from Barracuda (Mail Security Gateway). We use pfSense as a firewall. I am now supposed to send out over 10 IP addresses from our AntiSpam appliance. Basically, this works perfectly (outgoing NAT via RoundRobin). My main problem is currently that the firewall correctly increases the IP address with each new connection, but also always sends out the host name of the appliance with antispam.domain.com. The problem: if we send out over 10 IP addresses, I can always only use antispam.domain.com as reverse DNS. As soon as I enter ip1.antispam.domain.com as reverse DNS for IP 1, the emails are rejected (of course, since the AntiSpam system always sends out via antispam.domain.com).

I hope to find a solution with HAProxy here. It would be best if I send the AntiSpam system via a smarthost, which will then also The host name ip1.antispam.domain.com (ip2.antispam.domain.com), … rewritet is sent via IP 1.

Is this possible with HAProxy?

If I currently only use antispam.domain.com as reverse DNS for all IP addresses, I get an INVALID RDNS error back. Therefore every connection that is established must be sent out via the correct host name.

i can install the HAproxy Package on my pfSense firewall.

Thank you in advance.