Email server monitoring - response time

As I found POP3 monitoring works with different threshold times than what can be configured through Threshold Profile. Its critical response time is 2000ms and I can not change it. Beyond this value AppManager declares that the mail server is not available, therefore the response time is not displayed. My goal is to measure the round trip time of a message sent through the mail server to a mail server outside of the office and forwarded back to the office. Now the system virtually works fine, however, the POP3 fetching finds the previous test message in the mailbox produced a false response time. In this scenario, it seems the response time would greater than 2000ms.
Is there any solution to change the fetching threshold time?
ZKallo