Known hosts include trusted mail transfer agents (MTAs) and
the Cloud Pre-Filter that are deployed before
IMSS on your
network. If your
IMSS is deployed at the Internet gateway,
you do not need to specify known hosts. Use the known host settings in either of the
following
situations:
-
If you have one or multiple MTAs configured upstream from IMSS on your network, enable the known host setting and add
these MTAs as known hosts. IMSS then traces the nearest
upstream MTA that is not in the known host list and queries its IP address against
the email
reputation database as well as the IP Profiler approved and blocked lists.
For example, if you have MTA2 configured before IMSS on
your network and MTA1 outside your network deployed before MTA2, enable the known
host setting
and add MTA2 as a known host. IMSS then uses the IP
address of MTA1 for query.
-
If your IMSS is deployed behind the Cloud Pre-Filter,
enable the known host setting. By default, the Cloud Pre-Filter IP address is in the
known host
list.
If your network has upstream MTAs or the Cloud Pre-Filter deployed before IMSS, use the known host settings for the following
reasons:
-
IMSS regards all external email messages as coming from
these MTAs or the Cloud Pre-Filter and uses their IP addresses for query. All mail
traffic
routed through these IP addresses will then be considered safe.
-
IMSS considers these IP addresses as spam sources since
all spam messages come from these addresses before they arrive at IMSS in the mail flow.
 |
Note
IMSS synchronizes Cloud Pre-Filter IP addresses to the
known host list at 03:00 a.m. every day. These known hosts will not appear on the
management
console.
|
