diff --git a/offlineimap/folder/Base.py b/offlineimap/folder/Base.py
index 58f4fcd..f871d6f 100644
--- a/offlineimap/folder/Base.py
+++ b/offlineimap/folder/Base.py
@@ -302,7 +302,15 @@ class BaseFolder:
 
         with open(uidfilename + ".tmp", "wt") as uidfile:
             uidfile.write("%d\n" % newval)
-        os.rename(uidfilename + ".tmp", uidfilename)
+
+        # This is weird, os.rename on Windows raises an exception,
+        # But not in Linux. In linux the file is overwritten.
+        try:
+            os.rename(uidfilename + ".tmp", uidfilename)
+        except WindowsError:
+            os.remove(uidfilename)
+            os.rename(uidfilename + ".tmp", uidfilename)
+
         self._base_saved_uidvalidity = newval
 
     def get_uidvalidity(self):
diff --git a/offlineimap/folder/GmailMaildir.py b/offlineimap/folder/GmailMaildir.py
index 1dfccc7..15c7623 100644
--- a/offlineimap/folder/GmailMaildir.py
+++ b/offlineimap/folder/GmailMaildir.py
@@ -183,7 +183,7 @@ class GmailMaildirFolder(MaildirFolder):
             os.rename(tmppath, filepath)
         except OSError as e:
             raise OfflineImapError("Can't rename file '%s' to '%s': %s" %
-                                   (tmppath, filepath, e[1]),
+                                   (tmppath, filepath, e.errno),
                                    OfflineImapError.ERROR.FOLDER,
                                    exc_info()[2])
 
diff --git a/offlineimap/folder/Maildir.py b/offlineimap/folder/Maildir.py
index 3df4afa..f319b66 100644
--- a/offlineimap/folder/Maildir.py
+++ b/offlineimap/folder/Maildir.py
@@ -470,7 +470,7 @@ class MaildirFolder(BaseFolder):
             except OSError as e:
                 raise OfflineImapError(
                     "Can't rename file '%s' to '%s': %s" %
-                    (oldfilename, newfilename, e[1]),
+                    (oldfilename, newfilename, e.errno),
                     OfflineImapError.ERROR.FOLDER,
                     exc_info()[2])
 
@@ -556,7 +556,7 @@ class MaildirFolder(BaseFolder):
                     except OSError as e:
                         raise OfflineImapError(
                             "Can't rename file '%s' to '%s': %s" %
-                            (filename, newfilename, e[1]),
+                            (filename, newfilename, e.errno),
                             OfflineImapError.ERROR.FOLDER,
                             exc_info()[2])
 
diff --git a/offlineimap/imaplibutil.py b/offlineimap/imaplibutil.py
index b29b019..5f6f6f9 100644
--- a/offlineimap/imaplibutil.py
+++ b/offlineimap/imaplibutil.py
@@ -15,7 +15,6 @@
 #    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 import datetime
 import os
-import fcntl
 import time
 import subprocess
 import threading
@@ -29,6 +28,14 @@ from offlineimap import OfflineImapError
 from offlineimap.ui import getglobalui
 from imaplib2 import IMAP4, IMAP4_SSL, InternalDate
 
+try:
+    import portalocker
+except:
+    try:
+        import fcntl
+    except:
+        pass  # Ok if this fails, we can do without.
+
 
 class UsefulIMAPMixIn:
     def __getselectedfolder(self):
diff --git a/offlineimap/init.py b/offlineimap/init.py
index 9f9592e..fe7aaae 100644
--- a/offlineimap/init.py
+++ b/offlineimap/init.py
@@ -26,6 +26,7 @@ import collections
 from optparse import OptionParser
 
 import offlineimap
+from offlineimap.utils.distro_utils import get_os_name
 import imaplib2 as imaplib
 
 # Ensure that `ui` gets loaded before `threadutil` in order to
@@ -72,7 +73,18 @@ class OfflineImap:
     """
 
     def get_env_info(self):
-        info = "imaplib2 v%s, Python v%s" % (imaplib.__version__, PYTHON_VERSION)
+        # Transitional code between imaplib2 versions
+        try:
+            # imaplib2, previous versions, based on Python 2.x
+            l_imaplib_version = imaplib.__version__
+        except AttributeError:
+            # New imaplib2, version >= 3.06
+            l_imaplib_version = imaplib.version()
+        except:
+            # This should not happen
+            l_imaplib_version = " Unknown"
+
+        info = "imaplib2 v%s, Python v%s" % (l_imaplib_version, PYTHON_VERSION)
         try:
             import ssl
             info = "%s, %s" % (info, ssl.OPENSSL_VERSION)
@@ -446,13 +458,16 @@ class OfflineImap:
 
         try:
             self.num_sigterm = 0
-            signal.signal(signal.SIGHUP, sig_handler)
-            signal.signal(signal.SIGUSR1, sig_handler)
-            signal.signal(signal.SIGUSR2, sig_handler)
-            signal.signal(signal.SIGABRT, sig_handler)
-            signal.signal(signal.SIGTERM, sig_handler)
-            signal.signal(signal.SIGINT, sig_handler)
-            signal.signal(signal.SIGQUIT, sig_handler)
+
+            # We cannot use signals in Windows
+            if get_os_name() != 'windows':
+                signal.signal(signal.SIGHUP, sig_handler)
+                signal.signal(signal.SIGUSR1, sig_handler)
+                signal.signal(signal.SIGUSR2, sig_handler)
+                signal.signal(signal.SIGABRT, sig_handler)
+                signal.signal(signal.SIGTERM, sig_handler)
+                signal.signal(signal.SIGINT, sig_handler)
+                signal.signal(signal.SIGQUIT, sig_handler)
 
             # Various initializations that need to be performed:
             activeaccounts = self._get_activeaccounts(options)