[CentOS] yum update (first in a long time) - /var/log/dovecot no longer used

Thu May 5 14:07:17 UTC 2016
Gary Stainburn <gary at ringways.co.uk>

Me again,

Another change to my Centos 7.2 system since my 'yum update' yesterday is 
that /var/log/dovecot is no longer written to.

If I do 'systemctl status dovecot' I can see log entries. How can I now do the 
equiv or 'tail -f <logfile>'

Also, why has this changed, and where is it documented?