[CentOS] rsyslog.conf - why the "-" in this entry? mail.* -/var/log/maillog

In dealing with an unrelated issue I came across this in rsyslog.conf.

# The authpriv file has restricted access. authpriv.* /var/log/secure # Log all the mail messages in one place. mail.* -/var/log/maillog # Log cron stuff cron.* /var/log/cron

Why is there a "-" before /var/log/maillog? This character is not present before any of the other log files specified in /etc/rsyslog.conf. I have looked in the documents to discover the purpose of the leading "-" character in the mail log file specification but either I missed the reference or it is not there to be found.