Message Headers - X-SEF-Processed

Message Headers - X-SEF-Processed I'm just trying to work out why there has been a delay on an incoming email and I have been checking the headers, and was puzzled by this line:
Asked by: Guest \| Views: 240

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Guest [Entry]

"This actually relates to the Surfcontrol email software that scanned the email in question.

Format is :-

X-SEF-Processed: Surfcontrol / Websense version, Date and Time."