Messagelabs customers are unable to email another client of the ESS when their domain is still active but pointing to another vendor's MX records.
Error received : "421 4.4.0 [internal] no mail servers for this domain could be reached at this time" This error is common, but mostly will be seen in such a scenario.
The receiving domain is not using the clusters assigned to them initially, but they are pointing to a different MX records.
There are 2 solutions in order to quickly resolve the Issue :
1 - The recipient's domain owner or Admin should remove the domain from the client net portal, if they are sure that the domain will not be using our services.
2 - The domain should be using our MX records as assigned to them during the provisioning process
Note : In case when the client is not willing to use our services and they would like to cancel it , they are advised to contact our Cancellation Team.
KB will explain the required steps in order to cancel a service.