Update comments/blurb

Author: henryivesjones

Lib/test/test_email/test_generator.py

@@ -314,7 +314,9 @@ def _patch_random_randrange(*args, **kwargs):
             msg = MIMEMultipart()
             msg.attach(MIMEText(boundary_in_part))
             self.genclass(self.ioclass()).flatten(msg, linesep=linesep)
-            # .0 is appended if the boundary was found.
+            # Generator checks the message content for the string it is about
+            # to use as a boundary ('token' in this test) and when it finds it
+            # in our attachment appends .0 to make the boundary it uses unique.
             self.assertEqual(msg.get_boundary(), boundary + ".0")
 
     def test_lf_boundary_detection(self):

Misc/NEWS.d/next/Library/2026-04-07-14-13-40.gh-issue-148192.34AUYQ.rst

@@ -1,2 +1,3 @@
-``email.generator.Generator._make_boundary`` now correctly finds the
-boundary when using CRLF linesep.
+``email.generator.Generator._make_boundary`` could fail to detect a duplicate
+boundary string if linesep was not \n. It now correctly detects boundary
+strings when linesep is \r\n as well.