How to Exclude a Domain Entry after Enabling a 'Reject Message If Originator's Domain Has No MX Entry' Policy as an Antispam Method

For a SMTP acceptance/routing policy that will exclude a domain, in our example named example.org, from the currently enforced Reject message if originator's domain has no MX entry policy you should access from WebAdmin-> Security & Filtering-> Acceptance & Routing, the Advanced Settings section and select Add Acceptance / Routing rule.
From this new section you should:
Define a suggestive name for this rule for ease of tracking the action enforced.

In the Conditions area you should make sure that this rule is applied For incoming messages that match ALL of the conditions
Next, you should add the following two conditions:
Sender->domain add this rule and configure it to match the given domain, in our case example.org
For the second rule, select DNS Checks->Sender MX  and make sure to set this to Fail.

From the Actions section add the following entry:
SMTP->action and set this to Accept
Please note that the Explanation section is optional for this setting.

After saving the configuration by selecting the Save Configuration button, the new rule will accept e-mails from the given domain, in this particular case example.org, even if such e-mails fail the enforced MX checks.