fixup! Stop incorrectly RFC 2047 encoding non-ASCII email addresses

- Incorporate PR feedback
- Tailor blurbs to individual issues

Author: medmunds

Lib/email/_header_value_parser.py

@@ -2846,8 +2846,8 @@ def _refold_parse_tree(parse_tree, *, policy):
                 want_encoding = False
             else:
                 raise errors.InvalidMailboxError(
-                    "Non-ASCII address requires policy with utf8=True:"
-                    " '{}'".format(part)
+                    f"Non-ASCII mailbox '{part}' is invalid"
+                    " under current policy setting (utf8=False)"
                 )
 
         if want_encoding and not wrap_as_ew_blocked:

Misc/NEWS.d/next/Library/2024-07-31-17-22-10.gh-issue-83938.TtUa-c.rst

@@ -1,5 +1,8 @@
-The :mod:`email` module no longer incorrectly encodes non-ASCII characters
-in email addresses using :rfc:`2047` encoding. Under a policy with ``utf8=True``
-this means the addresses will be correctly passed through. Under a policy with
-``utf8=False``, attempting to serialize a message with non-ASCII email addresses
-will now result in an :exc:`~email.errors.InvalidMailboxError`.
+The :mod:`email` module no longer incorrectly uses :rfc:`2047` encoding for
+a mailbox with non-ASCII characters in its domain. Under a policy with
+:attr:`~email.policy.EmailPolicy.utf8` set ``False``, attempting to serialize
+such a message will now raise an :exc:`~email.errors.InvalidMailboxError`.
+Either apply an appropriate IDNA encoding to convert the domain to ASCII before
+serialization, or use :data:`email.policy.SMTPUTF8` (or another policy with
+``utf8=True``) to correctly pass through the internationalized domain name
+as Unicode characters.

Misc/NEWS.d/next/Library/2024-07-31-17-23-06.gh-issue-122476.TtUa-c.rst

@@ -1,5 +1,7 @@
-The :mod:`email` module no longer incorrectly encodes non-ASCII characters
-in email addresses using :rfc:`2047` encoding. Under a policy with ``utf8=True``
-this means the addresses will be correctly passed through. Under a policy with
-``utf8=False``, attempting to serialize a message with non-ASCII email addresses
-will now result in an :exc:`~email.errors.InvalidMailboxError`.
+The :mod:`email` module no longer incorrectly uses :rfc:`2047` encoding for
+a mailbox with non-ASCII characters in its local-part. Under a policy with
+:attr:`~email.policy.EmailPolicy.utf8` set ``False``, attempting to serialize
+such a message will now raise an :exc:`~email.errors.InvalidMailboxError`.
+There is no valid 7-bit encoding for an internationalized local-part. Use
+:data:`email.policy.SMTPUTF8` (or another policy with ``utf8=True``) to
+correctly pass through the local-part as Unicode characters.