diff --git a/dkim/__init__.py b/dkim/__init__.py
index a8d3bbe..b0b5721 100644
--- a/dkim/__init__.py
+++ b/dkim/__init__.py
@@ -365,7 +365,7 @@ def text(s):
     return s.encode('ascii')
 
 
-def fold(header, namelen=0):
+def fold(header, namelen=0, linesep=b'\r\n'):
     """Fold a header line into multiple crlf-separated lines at column 72.
 
     >>> text(fold(b'foo'))
@@ -399,10 +399,10 @@ def fold(header, namelen=0):
         i = header[:maxleng].rfind(b" ")
         if i == -1:
             j = maxleng
-            pre += header[:j] + b"\r\n "
+            pre += header[:j] + linesep + b" "
         else:
             j = i + 1
-            pre += header[:i] + b"\r\n "
+            pre += header[:i] + linesep + b" "
         header = header[j:]
         maxleng = 72
     if len(header) > 2:
@@ -460,8 +460,9 @@ class DomainSigner(object):
   #: (with either \\n or \\r\\n line endings)
   #: @param logger: a logger to which debug info will be written (default None)
   #: @param signature_algorithm: the signing algorithm to use when signing
+  #: @param linesep: use this line seperator for folding the headers
   def __init__(self,message=None,logger=None,signature_algorithm=b'rsa-sha256',
-        minkey=1024):
+        minkey=1024, linesep=b'\r\n'):
     self.set_message(message)
     if logger is None:
         logger = get_default_logger()
@@ -482,6 +483,9 @@ class DomainSigner(object):
     #: Minimum public key size.  Shorter keys raise KeyFormatError. The
     #: default is 1024
     self.minkey = minkey
+    # use this line seperator for output
+    self.linesep = linesep
+
 
   #: Header fields to protect from additions by default.
   #:
@@ -608,7 +612,7 @@ class DomainSigner(object):
 
     header_value = b"; ".join(b"=".join(x) for x in fields)
     if not standardize:
-      header_value = fold(header_value, namelen=len(header_name))
+      header_value = fold(header_value, namelen=len(header_name), linesep=b'\r\n')
     header_value = RE_BTAG.sub(b'\\1',header_value)
     header = (header_name, b' ' + header_value)
     h = HashThrough(self.hasher())
@@ -634,10 +638,10 @@ class DomainSigner(object):
     # relaxed/simple (for broken receivers), and fold now.
     idx = [i for i in range(len(fields)) if fields[i][0] == b'b'][0]
     fields[idx] = (b'b', base64.b64encode(bytes(sig2)))
-    header_value = b"; ".join(b"=".join(x) for x in fields) + b"\r\n"
+    header_value = b"; ".join(b"=".join(x) for x in fields) + self.linesep
 
     if not standardize:
-      header_value = fold(header_value, namelen=len(header_name))
+      header_value = fold(header_value, namelen=len(header_name), linesep=self.linesep)
 
     return header_value
 
@@ -947,7 +951,7 @@ class ARC(DomainSigner):
     results_lists = [raw.replace(srv_id + b';', b'').strip() for (raw, parsed) in auth_headers]
     results_lists = [tags.split(b';') for tags in results_lists]
     results = [tag.strip() for sublist in results_lists for tag in sublist]
-    auth_results = srv_id + b'; ' + b';\r\n  '.join(results)
+    auth_results = srv_id + b'; ' + (b';' + self.linesep + b'  ').join(results)
 
     # extract cv
     parsed_auth_results = AuthenticationResultsHeader.parse('Authentication-Results: ' + auth_results.decode('utf-8'))
@@ -1216,7 +1220,8 @@ class ARC(DomainSigner):
 def sign(message, selector, domain, privkey, identity=None,
          canonicalize=(b'relaxed', b'simple'),
          signature_algorithm=b'rsa-sha256',
-         include_headers=None, length=False, logger=None):
+         include_headers=None, length=False, logger=None,
+         linesep=b'\r\n'):
     # type: (bytes, bytes, bytes, bytes, bytes, tuple, bytes, list, bool, any) -> bytes
     """Sign an RFC822 message and return the DKIM-Signature header line.
     @param message: an RFC822 formatted message (with either \\n or \\r\\n line endings)
@@ -1229,11 +1234,12 @@ def sign(message, selector, domain, privkey, identity=None,
     @param include_headers: a list of strings indicating which headers are to be signed (default all headers not listed as SHOULD NOT sign)
     @param length: true if the l= tag should be included to indicate body length (default False)
     @param logger: a logger to which debug info will be written (default None)
+    @param linesep: use this line seperator for folding the headers
     @return: DKIM-Signature header field terminated by \\r\\n
     @raise DKIMException: when the message, include_headers, or key are badly formed.
     """
 
-    d = DKIM(message,logger=logger,signature_algorithm=signature_algorithm)
+    d = DKIM(message,logger=logger,signature_algorithm=signature_algorithm,linesep=linesep)
     return d.sign(selector, domain, privkey, identity=identity, canonicalize=canonicalize, include_headers=include_headers, length=length)
 
 
@@ -1260,7 +1266,7 @@ dkim_verify = verify
 def arc_sign(message, selector, domain, privkey,
              srv_id, signature_algorithm=b'rsa-sha256',
              include_headers=None, timestamp=None,
-             logger=None, standardize=False):
+             logger=None, standardize=False, linesep=b'\r\n'):
     # type: (bytes, bytes, bytes, bytes, bytes, bytes, list, any, any, bool) -> list
     """Sign an RFC822 message and return the ARC set header lines for the next instance
     @param message: an RFC822 formatted message (with either \\n or \\r\\n line endings)
@@ -1272,11 +1278,12 @@ def arc_sign(message, selector, domain, privkey,
     @param include_headers: a list of strings indicating which headers are to be signed (default all headers not listed as SHOULD NOT sign)
     @param timestamp: the time in integer seconds when the message is sealed (default is int(time.time) based on platform, can be string or int)
     @param logger: a logger to which debug info will be written (default None)
+    @param linesep: use this line seperator for folding the headers
     @return: A list containing the ARC set of header fields for the next instance
     @raise DKIMException: when the message, include_headers, or key are badly formed.
     """
 
-    a = ARC(message,logger=logger,signature_algorithm=b'rsa-sha256')
+    a = ARC(message,logger=logger,signature_algorithm=b'rsa-sha256',linesep=linesep)
     if not include_headers:
         include_headers = a.default_sign_headers()
     return a.sign(selector, domain, privkey, srv_id, include_headers=include_headers,
diff --git a/dkim/arcsign.py b/dkim/arcsign.py
index 2d668b9..ff5a263 100644
--- a/dkim/arcsign.py
+++ b/dkim/arcsign.py
@@ -59,7 +59,7 @@ def main():
 
     #try:
     sig = dkim.arc_sign(message, selector, domain, open(privatekeyfile, "rb").read(),
-                   domain + ": none", cv)
+                   domain + ": none", cv, dkim.util.get_linesep(message))
     for line in sig:
         sys.stdout.write(line)
     sys.stdout.write(message)
diff --git a/dkim/dkimsign.py b/dkim/dkimsign.py
index 73f9de4..227b8eb 100644
--- a/dkim/dkimsign.py
+++ b/dkim/dkimsign.py
@@ -70,8 +70,8 @@ def main():
 
     message = sys.stdin.read()
     try:
-        d = dkim.DKIM(message,logger=logger,
-                      signature_algorithm=args.signalg)
+        d = dkim.DKIM(message,logger=logger, signature_algorithm=args.signalg,
+                      linesep=dkim.util.get_linesep(message))
         sig = d.sign(args.selector, args.domain, open(
                      args.privatekeyfile, "rb").read(), identity = args.identity,
                      canonicalize=canonicalize, include_headers=include_headers,
diff --git a/dkim/tests/test_dkim.py b/dkim/tests/test_dkim.py
index fbe241b..a94937c 100644
--- a/dkim/tests/test_dkim.py
+++ b/dkim/tests/test_dkim.py
@@ -46,6 +46,11 @@ class TestFold(unittest.TestCase):
         self.assertEqual(
             b"foo" * 24 + b"\r\n foo", dkim.fold(b"foo" * 25))
 
+    def test_linesep(self):
+        self.assertEqual(
+            b"foo" * 24 + b"\n foo", dkim.fold(b"foo" * 25, linesep=b"\n"))
+
+
 
 class TestSignAndVerify(unittest.TestCase):
     """End-to-end signature and verification tests."""
@@ -203,6 +208,17 @@ p=11qYAYKxCrfVS/7TyWQHOg7hcvPapiMlrwIaaPcHURo="""
                 res = d.verify(dnsfunc=self.dnsfunc5)
                 self.assertTrue(res)
 
+    def test_verifies_lflinesep(self):
+        # A message verifies after being signed.
+        for header_algo in (b"simple", b"relaxed"):
+            for body_algo in (b"simple", b"relaxed"):
+                sig = dkim.sign(
+                    self.message, b"test", b"example.com", self.key,
+                    canonicalize=(header_algo, body_algo), linesep=b"\n")
+                res = dkim.verify(sig + self.message, dnsfunc=self.dnsfunc)
+                self.assertFalse(b'\r\n' in sig)
+                self.assertTrue(res)
+
     def test_implicit_k(self):
         # A message verifies after being signed when k= tag is not provided.
         for header_algo in (b"simple", b"relaxed"):
diff --git a/dkim/tests/test_util.py b/dkim/tests/test_util.py
index e01b3b5..bf39566 100644
--- a/dkim/tests/test_util.py
+++ b/dkim/tests/test_util.py
@@ -22,6 +22,7 @@ from dkim.util import (
     DuplicateTag,
     InvalidTagSpec,
     parse_tag_value,
+    get_linesep,
     )
 
 
@@ -75,6 +76,30 @@ class TestParseTagValue(unittest.TestCase):
       self.assertEqual(len(sig),11)
 
 
+class TestGetLineSep(unittest.TestCase):
+    """Line seperator probing tests."""
+
+    def test_default(self):
+        self.assertEqual(
+            b'\r\n',
+            get_linesep(b'abc'))
+
+    def test_withcrlf(self):
+        self.assertEqual(
+            b'\r\n',
+            get_linesep(b'abc\r\n'))
+
+    def test_withlf(self):
+        self.assertEqual(
+            b'\n',
+            get_linesep(b'abc\n'))
+
+    def test_toosmall(self):
+        self.assertEqual(
+            b'\r\n',
+            get_linesep(b'a'))
+
+
 def test_suite():
     from unittest import TestLoader
     return TestLoader().loadTestsFromName(__name__)
diff --git a/dkim/util.py b/dkim/util.py
index 3d1f722..97b59c9 100644
--- a/dkim/util.py
+++ b/dkim/util.py
@@ -33,6 +33,7 @@ __all__ = [
     'InvalidTagSpec',
     'InvalidTagValueList',
     'parse_tag_value',
+    'get_linesep',
     ]
 
 
@@ -80,3 +81,8 @@ def get_default_logger():
     if not logger.handlers:
         logger.addHandler(NullHandler())
     return logger
+
+def get_linesep(msg):
+    if msg[-2:] != b'\r\n' and msg[-1:] == b'\n':
+        return b'\n'
+    return b'\r\n'