Since the Freshservice emails originate outside our email estate, we mark the email as "External Email", which was earlier done to reduce phishing. Since the Freshservice email is a legit email, we want to whitelist this source so the banner does not show up. We notice that the emails originate from 18.104.22.168 and the whois on this gives us o1.email.freshservice.com. One option is to whitelist the IP, however this would break when the IP changes.
I'm looking for something more concrete rather than IP maybe a hostname which may stay more stable.
Any ideas the hostname that we could use to whitelist ?