No notification sent for nrpe hosts

hi experts -
I have an NRPE service configured, and the log on the plugin machine shows alerts being sent for both the local and the remotely monitored machines :

[1266396694] SERVICE NOTIFICATION: yoav;ec2-72-44-37-142.compute-1.amazonaws.com;Current Load;WARNING;notify-service-by-email;WARNING - load average: 7.54, 8.10, 7.60
[1266404604] SERVICE NOTIFICATION: yoav;localhost; Current Load;CRITICAL;notify-service-by-email;CRITICAL - load average: 8.38, 6.13, 3.49

however the mail daemon (and my inbox…) show only the alerts for the local host:

Feb 17 11:03:28 ubuntu postfix/smtp[30821]: 4A72C2613A: to=<…>, relay=ALT1.ASPMX.L.GOOGLE.com[209.85.219.56]:25, delay=4.1, delays=0.06/0.01/0.38/3.7, dsn=2.0.0, status=sent (250 2.0.0 OK 1266404608 24si387571ewy.6)
Feb 17 11:08:25 ubuntu postfix/smtp[31536]: 32A402613A: to=<…>, relay=ASPMX.L.GOOGLE.com[74.125.113.27]:25, delay=1, delays=0.05/0.02/0.17/0.77, dsn=2.0.0, status=sent (250 2.0.0 OK 1266404905 27si5367129vws.58)
Feb 17 11:13:25 ubuntu postfix/smtp[32205]: 2ADE82613A: to=<…>, relay=ASPMX.L.GOOGLE.com[209.85.221.34]:25, delay=1.2, delays=0.04/0.01/0.27/0.87, dsn=2.0.0, status=sent (250 2.0.0 OK 1266405205 42si17855646qyk.113)

any ideas how such a thing can happen ?