Hi all,
We are sending emails fine but some are rejected from some SMTP domains withy the message below:
'450 4.7.0 Proxy session
setup failed on Frontend with '451 4.4.0 Primary target IP address responded
with: "554 5.7.1 Delivery not authorized no reverse DNS record exists for
your connecting IP address." Attempted failover to alternate host, but
that did not succeed. Either there are no alternate hosts, or delivery failed
to all alternate hosts. The last endpoint attempted was ....
I searched on the outbound email IP from one of my sent emails to an external email and it was not the MX record IP, it was the firewall IP that is why it is blocked (as some email systems check for reverse DNS entry that points to your email server and the firewall do not have one in public DNS). My question is how to solve this? Is it by simply adding a RDNS record in public DNS for the firewall IP to point to our mx record or changing the route traffic on firewall? What are all our options?
Note: SPF wizard states that there is no SPF record found but there is an A and MX record currently exist for this domain (our SMTP domain)