The cisco security gateway is connected to LDAP (AD) and we have no issues with mailflow.
The weird thing is that the original email was sent in 01-Dec-2014 - the cisco ironport has resurrected the email on 23-Aug-2018 and all of a sudden started to send critical LDAP failure alerts.
Logs--------
Message 2746890 original subject on injection: Undeliverable: Warning <System> mailgate02.network.local: The query NetworkLDAP.accept failed with result inquiry time...