The FQDN of the host that sent the message to syslog-ng as resolved by {{ site.product.short_name }} using DNS. If the message traverses several hosts, this is the last host in the chain.
The {{ site.product.short_name }} application uses the following procedure to determine the value of the {{ include.from }} macro:
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The {{ site.product.short_name }} application takes the IP address of the host sending the message.
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If the use-dns() option is enabled, {{ site.product.short_name }} attempts to resolve the IP address to a hostname. If it succeeds, the returned hostname will be the value of the {{ include.from }} macro. This value will be the FQDN of the host if the use-fqdn() option is enabled, but only the hostname if use-fqdn() is disabled.
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If the use-dns() option is disabled, or the address resolution fails, the {{ include.from }} macro will return the IP address of the sender host.
For details on using name resolution in {{ site.product.short_name }}, see Using name resolution in syslog-ng.