From aba98083e081411dac595976468ff90b7a31ec32 Mon Sep 17 00:00:00 2001
From: Christian Ullrich <chris@chrullrich.net>
Date: Sun, 29 Jun 2025 14:30:02 +0200
Subject: [PATCH 1/2] Do not generate empty encoded-words

Fixes #136052.
---
 Lib/email/_header_value_parser.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Lib/email/_header_value_parser.py b/Lib/email/_header_value_parser.py
index 91243378dc0441..90b7f82efd2093 100644
--- a/Lib/email/_header_value_parser.py
+++ b/Lib/email/_header_value_parser.py
@@ -3011,7 +3011,10 @@ def _fold_as_ew(to_encode, lines, maxlen, last_ew, ew_combine_allowed, charset,
             to_encode_word = to_encode_word[:-1]
             encoded_word = _ew.encode(to_encode_word, charset=encode_as)
             excess = len(encoded_word) - remaining_space
-        lines[-1] += encoded_word
+        # If encoding a single character pushes this line over the limit,
+        # give up on it and go to the next line.
+        if to_encode_word != "":
+            lines[-1] += encoded_word
         to_encode = to_encode[len(to_encode_word):]
         leading_whitespace = ''
 

From 65f60fdd1cd7eb45ca8058c95cd639e2fa315f56 Mon Sep 17 00:00:00 2001
From: Christian Ullrich <christian.ullrich@traditionsa.lu>
Date: Sun, 29 Jun 2025 15:26:04 +0200
Subject: [PATCH 2/2] Add NEWS

---
 .../next/Library/2025-06-29-15-25-56.gh-issue-136052.P1HgAD.rst  | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2025-06-29-15-25-56.gh-issue-136052.P1HgAD.rst

diff --git a/Misc/NEWS.d/next/Library/2025-06-29-15-25-56.gh-issue-136052.P1HgAD.rst b/Misc/NEWS.d/next/Library/2025-06-29-15-25-56.gh-issue-136052.P1HgAD.rst
new file mode 100644
index 00000000000000..5b4a46143e3d94
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-06-29-15-25-56.gh-issue-136052.P1HgAD.rst
@@ -0,0 +1 @@
+Do not create empty MIME encoded-words when preparing e-mail headers.