How can I avoid from adding an original hostname(or, IP address) to _SYSLOG_ROUGING event when forwarding a third party server?

[Masa]

How can I avoid from adding an original hostname(or, IP address) to _SYSLOG_ROUGING event when forwarding a third party server?

I can see that Splunk add host information to original syslog event when using _SYSLOG_ROUTING to forward syslog events to a third party server?

Below is an example added the server's IP address 192.168.10.111 which was already in the original event.

192.168.10.111 Mar 16 00:01:29 192.168.10.111 postfix/qmgr[1106]: EA11004022: from=, size=3514, nrcpt=1 (queue active) 

How can I remove the host name?

[Masa]

Probably you're using non-syslog sourcetype. In that case, try syslogSourceType attribute in outputs.conf. This should avoid adding the originated hostname.

syslogSourceType = <string>
* Specifies an additional rule for handling data, in addition to that 
  provided by the 'syslog' source type.
* This string is used as a substring match against the sourcetype key. For
  example, if the string is set to "syslog", then all sourcetypes
  containing the string 'syslog' receive this special treatment.
* To match a sourcetype explicitly, use the pattern
  "sourcetype::sourcetype_name".
    * Example: syslogSourceType = sourcetype::apache_common
* Data that is "syslog" or matches this setting is assumed to already be in 
  syslog format. 
* Data that does not match the rules has a header, optionally a timestamp 
  (if defined in 'timestampformat'), and a hostname added to the front of 
  the event. This is how Splunk software causes arbitrary log data to match syslog expectations.
* No default.

For more detail,
Official Doc:
https://docs.splunk.com/Documentation/Splunk/latest/Data/HowSplunkEnterprisehandlessyslogdata
Community Wiki: (old)
https://wiki.splunk.com/Community:Test:How_Splunk_behaves_when_receiving_or_forwarding_udp_data