Watchguard Firebox X1000 Reference Manual page 233

Logging tab
Reference Guide
Remove
Click to remove the selected item from the list above.
Don't substitute for these address patterns
Enter the addresses to appear "as is" outside the firewall.
Add
Click to add the new address pattern to the list.
Remove
Click to remove the selected item from the list above.
Masquerade Message IDs
When this feature is enabled, message IDs in the Message-ID and
Resent-Message-ID header fields are converted to a new ID
composed of an encoded version of the original ID, plus a time
stamp, plus the official host name entered in the Domain Name
field above.
Masquerade MIME boundary strings
When this feature is enabled, the firewall converts MIME
boundary strings in messages and attachments to a string that
does not reveal internal host names and other identifying strings.
Log removal of unknown headers
Click to log unknown headers that are filtered by the proxy.
Log Message-ID masquerading
Click to log the original and replacement Message-ID headers.
Log MIME masquerading
Logs the original and replacement MIME boundary strings, and
the replacement of the Content-Type header
Log domain masquerading
Click to log the original and replacement domains in HELO and
MAIL FROM commands.
Log accounting/auditing information
Click to log accounting and auditing information.
Policy Manager
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