help -- nmap not probing filtered ports

[Utkarsh Shrivastava <utkarsh12 () gmail com>]

Hi all,
 I am trying to identify if a host is up or not. Say, if I have received
email from IP x, I cannot ping IP x and check if it is up or not as
windows firewall prevents it by default. (works fine for linux hosts).
I've used virtually all the nmap options but not luck. nmap -PN <IP>
always tells me that the host is up
(because it treats in as *online*) and other options such as -sL, -sP,-sX
doesn't recognize it as active. I am sure IP x is up because I have received
 an email within a minute from it. Any pointers?

Thanks,
Utkarsh
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