How to print the "To:" address in virus reports?

[Jason Summers]

Maybe I'm doing something wrong, but the $to variable in files like
sender.virus.report.txt does not seem to expand to the "To:" SMTP header
as I would have expected. Is there another variable that I can use that
expands to the actual "To:" header?

Suppose tech-support at example.com is an alias that gets forwarded to
joe at internal-server.example.com. If someone then sends a virus to
tech-support at example.com, the warning message that the sender receives
from MailScanner (running on internal-server) will assert that they sent
a message "To: <joe at internal-server.example.com>". That's not correct,
and could even inappropriately leak information about your internal
network.

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Jason Summers