pop3.monitor question

[willem]

hostgroup mailservers 10.0.135.1

watch mailservers
     service pop
        interval 5m
        monitor pop3.monitor -p 25 -t 60
        period wd {Mon-Fri} hr {9am-12pm}
            alertafter 10m
            alertevery 1h
            alert mail.alert realother@localhost

what's wrong here? the above is my best gues but I tryed a lot. syslog
tells me:
Oct 23 14:23:02 localhost mon[24217]: failure for mailservers pop
1003839782 10.0.135.1

any Ideas?