DNS lookups never use UTF-8

[exim.git] / doc / doc-txt / experimental-spec.txt

diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt
index ce4edeb3d8c47bd5397593ff5505bb34083275e9..3dbf13f9da71910a2d9a847480cba19049b958d3 100644 (file)
--- a/doc/doc-txt/experimental-spec.txt
+++ b/doc/doc-txt/experimental-spec.txt
@@ -1276,6 +1276,29 @@ SMTPUTF8
 Internationalised mail name handling.
 RFCs 6530, 6533, 5890
 
+Compile with EXPERIMENTAL_INTERNATIONAL and libidn.
+
+Main config option smtputf8_advertise_hosts, default '*',
+a host list.  If this matches the sending host and
+accept_8bitmime is true (the default) then the ESMTP option
+SMTPUTF8 will be advertised.
+
+If the sender specifies the SMTPUTF8 option on a MAIL command
+international handling for the message is enabled and
+the expansion variable $message_smtputf8 will have value TRUE.
+
+The option allow_utf8_domains is set to true for this
+message. All DNS lookups are converted to a-label form
+whatever the setting of allow_utf8_domains.
+
+Log lines and Received-by: header lines will aquire a "utf8"
+prefix on the protocol element, eg. utf8esmtp.
+
+Expansion operators:
+       ${utf8_domain_to_alabel:str}
+       ${utf8_domain_from_alabel:str}
+       ${utf8_localpart_to_alabel:str}
+       ${utf8_localpart_from_alabel:str}
 
 
 --------------------------------------------------------------