[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.


-- 
***          E-Mail is NOT a SECURE channel          ***
James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
Harte & Lyne Limited          http://www.harte-lyne.ca
9 Brockley Drive              vox: +1 905 561 1241
Hamilton, Ontario             fax: +1 905 561 0757
Canada  L8E 3C3