Update custom-detection-rules.md

Author: ep3p

defender-xdr/custom-detection-rules.md

@@ -194,7 +194,7 @@ Near real-time detections are supported for the following tables:
 - `DeviceProcessEvents`
 - `DeviceRegistryEvents`
 - `EmailAttachmentInfo`
-- `EmailEvents` (except `LatestDeliveryLocation` and `LatestDeliveryAction` columns)
+- `EmailEvents` (except `LatestDeliveryLocation`, `LatestDeliveryAction` and `ExchangeTransportRule` columns)
 - `EmailPostDeliveryEvents`
 - `EmailUrlInfo`
 - `IdentityDirectoryEvents`