A very quick way to learn about a feature: in the GUI, navigate to the Network -> Incoming Relays page. Then, click the online help link in the upper-right of the page. The online help will be opened directly section that relates to that feature; it is context sensitive. (This technique works for all pages in the GUI.)
"The Incoming Relays Feature: Overview
"Occasionally, administrators need to run the IronPort appliance behind the mail exchange (MX) or mail transfer agent (MTA) at the edge of the network instead of receiving mail directly from the Internet. Unfortunately, when using this configuration the IronPort appliance is not receiving the mail directly from the Internet and so it does not have access to the last connecting IP address from the external network. Instead mail received is listed as being received from the local MX/MTA. It is critical for successful operation of the IronPort appliance that the connecting IP address be known so that SenderBase Reputation Service (SBRS) can be used in IronPort Anti‑Spam scanning.
"The solution is to configure an incoming relay. When configuring an incoming relay, you specify the names and IP addresses of all of the internal MX/MTAs connecting to the IronPort appliance, as well as the header used to store the originating IP address. You have two options for specifying the header: a custom header or an existing received header."
DocumentationCode download linksGoalRequirementLimitationsSupported ISR
and UCS-E ModelSupported ISRG2 and UCS-E Blades:Supported ISR4K and
UCS-E Blades:Step by Step ConfigurationConfigure one of the connectivity
options to access the Cisco IMC from the n...
Firepower Threat Defense (NGFWv) on UCS E-series - Transparent Mode in
HA DocumentationCode download linksGoalRequirementLimitationsSupported
ISR and UCS-E ModelSupported ISRG2 and UCS-E Blades:Supported ISR4K and
UCS-E Blades:Step by Step ConfigurationCo...
Question I am currently unable to specify "crypto keyring" command when
configuring VPN connection on my cisco 2901 router. The following
licenses have been activated on my router :