Having an error on one of my servers I was being spammed by an email, so I decided to create a filter for it to automatically delete it.

I decided to delete the email base on the subject (as I want to receive the rest of the emails from that sender).

So, I logged in the ISPConfig interface, got to Email -> Email Mailbox and clicked my mailbox. From there to Mail Filter and created a new filter with the following options: Source: Subject Contains Cron root@server2 root test -x /usr/sbin/tigercron && { [ -r "$DEFAULT" ] && . "$DEFAULT" ; nice -n$NICETIGER /usr/sbin/tigercron -q ; }

It's an error from one of the scripts of tiger (I reported it).

Then in my mail sever log I have this line: mail dovecot: lda(mymailbox@domain.com): Error: sieve: failed to open script /var/vmail/domain.com/mymailbox/.sieve (view user logfile /var/vmail/domain.com/mymailbox/.sieve.log for more information)

Looking in /var/vmail/domain.com/mymailbox/.sieve.log I found those lines over and over: sieve: info: started log at Sep 29 14:30:05. main script: line 6: error: invalid regular expression '.*Cron root@server2 root test -x /usr/sbin/tigercron && { [ -r "$DEFAULT" ] && . "$DEFAULT" ; nice -n$NICETIGER /usr/s...' for regex match: invalid content of {}. main script: error: validation failed.