Измеряем очередь Postfix
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#Postfix Mail Queue Size
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Target[postfix_queue]: `/usr/bin/sudo find /var/spool/postfix/deferred/ /var/spool/postfix/active/ /var/spool/postfix/maildrop/ -type f | wc -l && echo 0`
MaxBytes[postfix_queue]: 10000
Title[postfix_queue]: Postfix queue stats
PageTop[postfix_queue]: <H1>Postfix Queue Stats</H1>
YLegend[postfix_queue]: Postfix queue
ShortLegend[postfix_queue]: Msgs
Legend1[postfix_queue]: Messages in queue
LegendI[postfix_queue]: Messages :
LegendO[postfix_queue]:
Options[postfix_queue]: gauge,growright,nopercent,integer
натолкнул на мысль:
http://www.pyrosoft.co.uk/blog/2007/10/03/querying-postfixs-queue-size/