Hello, my qmail log file (/var/log/kloxo/maillog) contained many of these codes:

Apr  8 14:06:47 vps qmail: 1396958807.038127 starting delivery 380758: msg 436340219 to local [email protected]
Apr  8 14:06:47 vps qmail: 1396958807.038244 status: local 2/10 remote 0/60
Apr  8 14:06:47 vps qmail: 1396958807.078524 warning: trouble injecting bounce message, will try later
So i found someone adviced using this script: https://qmail.jms1.net/scripts/qfixq.shtml
and seeing if there is enough space on drive (df -h)

but im unsure if it fixed the issue