Unusual identity creation using exchange powershell

Original query, unchanged.

(union isfuzzy=true
(SecurityEvent
| where EventID==4688
| where CommandLine has_any ("New-Mailbox","Update-RoleGroupMember") and CommandLine has "HealthMailbox55x2yq"
| project TimeGenerated, DeviceName = Computer, AccountName = SubjectUserName, AccountDomain = SubjectDomainName, ProcessName, ProcessNameFullPath = NewProcessName, EventID, Activity, CommandLine, EventSourceName, Type
| extend InitiatingProcessAccount = strcat(AccountDomain, "\\", AccountName)
),
(DeviceProcessEvents
| where ProcessCommandLine has_any ("New-Mailbox","Update-RoleGroupMember") and ProcessCommandLine has "HealthMailbox55x2yq"
| extend timestamp = TimeGenerated, AccountDomain = InitiatingProcessAccountDomain, AccountName = InitiatingProcessAccountName
| extend InitiatingProcessAccount = strcat(AccountDomain, "\\", AccountName)
)
)
| extend HostName = tostring(split(DeviceName, ".")[0]), DomainIndex = toint(indexof(DeviceName, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(DeviceName, DomainIndex + 1), DeviceName)