Delayed Mail (still being retried)

This is the Symantec Mail Security program at host usfmercury1.usfood.com.

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# THIS IS A WARNING ONLY. YOU DO NOT NEED TO RESEND YOUR MESSAGE. #
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Your message could not be delivered for 4.0 hours.
It will be retried until it is 5.0 days old.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                        The Symantec Mail Security program

<rx37300roxie.medley_at_usfood.com>: delivery temporarily suspended: unknown mail
    transport error