Digital Guardian - Bulk exfiltration to external domain

let threshold = 10;
let corp_domain = dynamic(['example.com']);
DigitalGuardianDLPEvent
| where NetworkApplicationProtocol =~ 'SMTP'
| where isnotempty(inspected_document)
| extend s_domain = extract(@'@(.*)', 1, SrcUserName)
| extend d_domain = extract(@'@(.*)', 1, DstUserName)
| where s_domain in~ (corp_domain)
| where d_domain !in (corp_domain)
| summarize f = dcount(inspected_document) by SrcUserName, DstUserName, bin(TimeGenerated, 30m)
| where  f >= threshold
| extend AccountCustomEntity = SrcUserName