port-i386/52404: Date of User mail in mail directory sometimes shows "Jan 1 1970"

[MMichael%Nareg.Com.AU@localhost]

>Number:         52404
>Category:       port-i386
>Synopsis:       Date of User mail in mail directory sometimes shows "Jan 1 1970"
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    port-i386-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Jul 15 02:25:00 +0000 2017
>Originator:     Michael Ghougassian
>Release:        NetBSD-7.1-i386-install.img.gz
>Organization:
Nareg Internet Pty Ltd
>Environment:
NetBSD one.nareg.com.au 7.1 NetBSD 7.1 (GENERIC.201703111743Z) i386
>Description:
In mail directory ls -al shows the following:
-rw------ 1 USERNAME wheel  size Jan 1  1970   USERNAME

About 10% of the users show this invalid date "sometimes" and is not specific to a USERNAME it keeps changing and ALSO while there is no mail activity.
>How-To-Repeat:
It randomly appears different while running

ls -al ; sleep 15

>Fix:
very random and critical as I look for date change to detect arrival of new mail