Index: Lib/email/test/test_email.py
===================================================================
--- Lib/email/test/test_email.py	(revision 74225)
+++ Lib/email/test/test_email.py	(working copy)
@@ -18,6 +18,7 @@
 from email.charset import Charset
 from email.header import Header, decode_header, make_header
 from email.parser import Parser, HeaderParser
+from email.feedparser import BufferedSubFile, NeedMoreData
 from email.generator import Generator, DecodedGenerator
 from email.message import Message
 from email.mime.application import MIMEApplication
@@ -2510,6 +2511,37 @@
         eq(msg.get('Header'), value1)
         eq(msg.get('Next-Header'), value2)
 
+    def test_detect_microsoft_linebreak_at_end_of_chunk(self):
+        # Addresses: [ 1721862 ] email.FeedParser.BufferedSubFile
+        # improperly handles "\r\n"
+        # Test code based on example provided by Sye van der Veen.
+        # First line contains previously buggy data; second and third must
+        # continue to pass, post-alteration.
+        input = "1\r\n10\r\n100\r\n1000\r\n10000\r\n" + \
+         "1\r10\r100\r1000\r10000\r" + \
+         "1\n10\n100\n1000\n10000\n"
+        data = StringIO(input)
+        results = []
+        buffered_sub_file = BufferedSubFile()
+        while True:
+            sample = data.read(3) # Read the next three characters.
+            if not sample:
+                break
+                
+            buffered_sub_file.push(sample)
+            for line in buffered_sub_file:
+                if line is NeedMoreData:
+                    break
+                else:
+                    results.append(line)
+        buffered_sub_file.close()
+        data.close()
+        
+        targets = ['1' + target for target in input.split('1')[1:]]
+        assert len(results) == len(targets)
+        for (result, target) in zip(results, targets):
+            assert result == target
+
     def test_rfc2822_header_syntax(self):
         eq = self.assertEqual
         m = '>From: foo\nFrom: bar\n!"#QUX;~: zoo\n\nbody'
Index: Lib/email/feedparser.py
===================================================================
--- Lib/email/feedparser.py	(revision 74225)
+++ Lib/email/feedparser.py	(working copy)
@@ -26,6 +26,8 @@
 from email import errors
 from email import message
 
+NLC_mac = '\r'
+NLC_unix = '\n'
 NLCRE = re.compile('\r\n|\r|\n')
 NLCRE_bol = re.compile('(\r\n|\r|\n)')
 NLCRE_eol = re.compile('(\r\n|\r|\n)$')
@@ -98,12 +100,28 @@
         # Handle any previous leftovers
         data, self._partial = self._partial + data, ''
         # Crack into lines, but preserve the newlines on the end of each
+        # First, the possibility that the data was split in the middle of a
+        # Microsoft linebreak must be addressed.
+        if data.endswith(NLC_mac):
+            split_point = max(
+             data[:-len(NLC_mac)].rfind(NLC_mac),
+             data.rfind(NLC_unix)
+            )
+            if split_point > -1:
+                # Treat everything after the last sure split-point as partial.
+                self._partial = data[split_point + 1:]
+                data = data[:split_point + 1]
+            else:
+                # Treat the entire line as partial data and abort.
+                self._partial = data
+                return
         parts = NLCRE_crack.split(data)
         # The *ahem* interesting behaviour of re.split when supplied grouping
         # parentheses is that the last element of the resulting list is the
         # data after the final RE.  In the case of a NL/CR terminated string,
         # this is the empty string.
-        self._partial = parts.pop()
+        if not self._partial: # Partial data may have been set earlier.
+            self._partial = parts.pop()
         # parts is a list of strings, alternating between the line contents
         # and the eol character(s).  Gather up a list of lines after
         # re-attaching the newlines.