[ci skip] Use INTL_IDNA_VARIANT_UCS46 to convert non-ASCII domain names in emails

Close #5300
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index d222e17..647fe48 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -7,6 +7,11 @@
 
 Release Date: Not Released
 
+-  General Changes
+
+   -  Updated :doc:`Form Validation Library <libraries/form_validation>` rule ``valid_email`` to use ``INTL_IDNA_VARIANT_UCS46`` for non-ASCII domain names.
+   -  Updated :doc:`Email Library <libraries/email>` to use ``INTL_IDNA_VARIANT_UCS46`` for non-ASCII domain names.
+
 Bug fixes for 3.1.7
 -------------------