The following packages will be installed:
 postgrey 
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You must have the nobody user and nogroup group
in
order to build postgrey.  Sample lines to do so are below:
# groupadd -g 99 nogroup
# useradd -u 98 -d /var/lib/postgrey -s /bin/false -g nogroup nobody
Exiting...

fakeroot -- sh postgrey.SlackBuild Failed