Where an event is ingested via import the import job can be configured to use either the process timestamp or the event timestamp. This is achieved by editing the import configuration file (i.e. import.ini) and adding the following syntax (Defaults to Yes):
EMail.EventDateFromEMail=Yes or No
If this parameter is set to 'Yes' the timestamp reflects the time and date in the email, based on the delivery time or time sent, if the email does not contain the delivery time or time sent, the Event Import process sets the timestamp to the time of import.
If this parameter is set to 'No', the timestamp reflects the time of import.