System stopped postfix with force

Hi folks,

this happend tonight with my mailinabox server v0.23a
Why can this happen?

Nov 16 02:56:15 box postfix/anvil[23671]: statistics: max cache size 1 at Nov 16 02:52:54
Nov 16 03:00:01 box postfix/submission/smtpd[24051]: connect from[]
Nov 16 03:00:02 box postfix/master[17258]: terminating on signal 15
Nov 16 03:00:07 box postfix/postfix-script[24479]: warning: stopping the Postfix mail system with force

afterwards postfix was down, not restarted and nobody could sent mails anymore