Just to be sure:
Unless you did a signal-event reconfigure; signal-event reboot (or a reconfigure in the server-manager) after the update you should report it as a bug, if you did not do so, you just left out part of the update procedure and it would be a user error and not a bug.
I did a manual yum update on the command line logged in as root.
I checked the command line history. I did:
yum update
signal-event post-upgrade; signal-event reboot
This is what yum reports to do next after an update (to be exact: I copied yum output and pasted it back to the command line)
This is what I get when I enter signal-event reconfigure on the commandline:
signal-event reconfigure
Can't open directory /etc/e-smith/events/reconfigure
I am sure I had to do the signal-event post-upgrade; signal-event reboot command twice to get webmail running again.