.option dkim_strict smtp string&!! unset
This option defines how Exim behaves when signing a message that
should be signed fails for some reason. When the expansion evaluates to
-either "1" or "true", Exim will defer. Otherwise Exim will send the message
+either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
variables here.
When unspecified, the header names listed in RFC4871 will be used,
whether or not each header is present in the message.
The default list is available for the expansion in the macro
-"_DKIM_SIGN_HEADERS".
+&"_DKIM_SIGN_HEADERS"&
+.new
+and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
+.wen
If a name is repeated, multiple headers by that name (or the absence thereof)
will be signed. The textually later headers in the headers part of the
message are signed first, if there are multiples.
-A name can be prefixed with either an '=' or a '+' character.
-If an '=' prefix is used, all headers that are present with this name
+A name can be prefixed with either an &"="& or a &"+"& character.
+If an &"="& prefix is used, all headers that are present with this name
will be signed.
-If a '+' prefix if used, all headers that are present with this name
+If a &"+"& prefix if used, all headers that are present with this name
will be signed, and one signature added for a missing header with the
name will be appended.