No mail notification on failed scheduled ant-builds

We use Continuum to trigger hourly ant scripts.

On a sheduled failed build we got no messages, the log looks like:

2011-04-19 13:16:08,738 [pool-1-thread-133] INFO org.apache.continuum.utils.shell.DefaultShellCommandHelper - Working directory: /data/continuum/data/working-directory/1
2011-04-19 13:20:44,589 [pool-1-thread-133] INFO org.apache.maven.continuum.execution.ant.AntBuildExecutor - Exit code: 1
2011-04-19 13:20:44,651 [pool-1-thread-133] INFO org.apache.maven.continuum.buildcontroller.DefaultBuildController - Performing action deploy-artifact
2011-04-19 13:20:44,930 [pool-1-thread-133] INFO org.apache.maven.continuum.notification.mail.MailContinuumNotifier - Message Subject: '[continuum] BUILD FAILURE: onewind - OnUniverse Standardbuild zu Workhours'.
2011-04-19 13:20:44,930 [pool-1-thread-133] INFO org.apache.maven.continuum.notification.mail.MailContinuumNotifier - Sending message: From '"Continuum@xxx" <continuum@server>'.
2011-04-19 13:20:44,930 [pool-1-thread-133] INFO org.apache.maven.continuum.notification.mail.MailContinuumNotifier - Recipient: To 'xxx@xxx.xxx.de'.
org.apache.maven.continuum.notification.mail.MailContinuumNotifier - No developers have been configured...notifcation email will not be sent

Wenn the some job is triggerd by a user the expected email is sent as expected. You will find the same logging except the info "No developers have been configured...notifcation email will not be sent"

How to configure continuum to sent emails?