The "backoffice-disable" setting:

If backoffice-disable is true, then the automatic backoffice
processing is disabled.  Automatic backoffice processing is the
backoffice work that normally runs after each web page is
rendered.  Backoffice processing that is triggered by the
"fossil backoffice" command is unaffected by this setting.

Backoffice processing does things such as delivering
email notifications.  So if this setting is true, and if
there is no cron job periodically running "fossil backoffice",
email notifications and other work normally done by the
backoffice will not occur.