/etc/amavis/en_US/template-auto-response.txt is in amavisd-new 1:2.10.1-2ubuntu1.
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# =============================================================================
# This is a template for the plain text part of an auto response (e.g.
# vacation, out-of-office), see RFC 3834.
#
From: %f
Date: %d
To: [? %#T |undisclosed-recipients:;|[%T|, ]]
[? %#C |#|Cc: [%C|, ]]
Reply-To: postmaster@%h
Message-ID: <ARE%i@%h>
Auto-Submitted: auto-replied
[:wrap|76||\t|Subject: Auto: autoresponse to: %s]
[? %m |#|In-Reply-To: %m]
Precedence: junk
This is an auto-response to a message \
[? %a |\nreceived on %d,|received from\nIP address \[%a\] on %d,]
envelope sender: %s
(author) From: [:rfc2822_from]
[? %j |#|[:wrap|78|| |Subject: %j]]
[?[:dkim|author]|#|
A first-party DKIM or DomainKeys signature is valid, d=[:dkim|author].]
|