X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/9604413b16bf7270395b92690ef429dca4a14eee..3203e7baa4148a7068bc69caef3b63dcb3971b92:/doc/doc-txt/experimental-spec.txt

diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt
index 1a0ece574..0eeb22758 100644
--- a/doc/doc-txt/experimental-spec.txt
+++ b/doc/doc-txt/experimental-spec.txt
@@ -436,6 +436,7 @@ dmarc_tld_file      Defines the location of a text file of valid
                     during domain parsing. Maintained by Mozilla,
                     the most current version can be downloaded
                     from a link at http://publicsuffix.org/list/.
+                    See also util/renew-opendmarc-tlds.sh script.
 
 Optional:
 dmarc_history_file  Defines the location of a file to log results
@@ -806,6 +807,24 @@ is used as a basis (you must have added one on entry to the ADMD).
 Expanded as a whole; if unset, empty or forced-failure then no signing is done.
 If it is set, all three elements must be non-empty.
 
+Caveats:
+ * There must be an Authentication-Results header, presumably added by an ACL
+   while receiving the message, for the same ADMD, for arc_sign to succeed.
+   This requires careful coordination between inbound and outbound logic.
+ * If passing a message to another system, such as a mailing-list manager
+   (MLM), between receipt and sending, be wary of manipulations to headers made
+   by the MLM.
+   + For instance, Mailman with REMOVE_DKIM_HEADERS==3 might improve
+     deliverability in a pre-ARC world, but that option also renames the
+     Authentication-Results header, which breaks signing.
+ * Even if you use multiple DKIM keys for different domains, the ARC concept
+   should try to stick to one ADMD, so pick a primary domain and use that for
+   AR headers and outbound signing.
+
+Signing is not compatible with cutthrough delivery; any (before expansion)
+value set for the option will result in cutthrough delivery not being
+used via the transport in question.
+
 
 
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