diff --git a/Lib/email/header.py b/Lib/email/header.py
index 3215a80f9b6..afcea404580 100644
--- a/Lib/email/header.py
+++ b/Lib/email/header.py
@@ -94,6 +94,9 @@ def decode_header(header):
             word = email.quoprimime.header_decode(encoded_string)
             decoded_words.append((word, charset))
         elif encoding == 'b':
+            paderr = len(encoded_string) % 4   # Postel's law: add missing padding
+            if paderr:
+                encoded_string += '==='[:4 - paderr]
             try:
                 word = email.base64mime.decode(encoded_string)
             except binascii.Error:
diff --git a/Lib/email/test/test_email.py b/Lib/email/test/test_email.py
index 7d91d25884e..05591422c23 100644
--- a/Lib/email/test/test_email.py
+++ b/Lib/email/test/test_email.py
@@ -1645,6 +1645,15 @@ Re: =?mac-iceland?q?r=8Aksm=9Arg=8Cs?= baz foo bar =?mac-iceland?q?r=8Aksm?=
                               (b'rg', None), (b'\xe5', 'iso-8859-1'),
                               (b'sbord', None)])
 
+    def test_rfc2047_B_bad_padding(self):
+        s = '=?iso-8859-1?B?%s?='
+        data = [                                # only test complete bytes
+            ('dm==', b'v'), ('dm=', b'v'), ('dm', b'v'),
+            ('dmk=', b'vi'), ('dmk', b'vi')
+          ]
+        for q, a in data:
+            dh = decode_header(s % q)
+            self.assertEqual(dh, [(a, 'iso-8859-1')])
 
 
 # Test the MIMEMessage class
@@ -3172,7 +3181,7 @@ A very long line that must get split to something other than at the
 
     def test_broken_base64_header(self):
         raises = self.assertRaises
-        s = 'Subject: =?EUC-KR?B?CSixpLDtKSC/7Liuvsax4iC6uLmwMcijIKHaILzSwd/H0SC8+LCjwLsgv7W/+Mj3IQ?='
+        s = 'Subject: =?EUC-KR?B?CSixpLDtKSC/7Liuvsax4iC6uLmwMcijIKHaILzSwd/H0SC8+LCjwLsgv7W/+Mj3I ?='
         raises(errors.HeaderParseError, decode_header, s)
 
 
diff --git a/Misc/ACKS b/Misc/ACKS
index 03f96ebf5c0..6486e794ca6 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -817,6 +817,7 @@ Felix Wiemann
 Gerry Wiener
 Frank Wierzbicki
 Bryce "Zooko" Wilcox-O'Hearn
+Jason Williams
 John Williams
 Sue Williams
 Gerald S. Williams
diff --git a/Misc/NEWS b/Misc/NEWS
index 8e164a9c3cb..262bd5e054e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -84,6 +84,9 @@ C-API
 Library
 -------
 
+- Issue #3196: email header decoding is now forgiving if an RFC2047
+  encoded word encoded in base64 is lacking padding.
+
 - Issue #8447: Make distutils.sysconfig follow symlinks in the path to
   the interpreter executable.  This fixes a failure of test_httpservers
   on OS X.