The Trend Micro Sender Filtering, which includes IP Profiler, Email Reputation and
SMTP Traffic
Throttling, blocks connections at the IP level.
To use Sender Filtering, any firewall between IMSS and the
edge of your network must not modify the connecting IP address as Sender Filtering
is
not compatible with networks using network address translation (NAT). If IMSS accepts SMTP connections from the same source
IP address, for instance, Sender Filtering will not work, as this address would be
the
same for every received message and the sender filtering software would be unable
to
determine whether the original initiator of the SMTP session was a known sender of
spam.