aptitude install ntp ntpdate
/etc/init.d/ntp stop
ntpdate -s ntpserver
/etc/init.d/ntp start

Pas envie de le retenir ^^

time /usr/bin/mailq | awk 'BEGIN {count=0} /^ .*@/ {count++} END{print count}'
123

real 0m0.013s
user 0m0.000s
sys 0m0.004s