diff --git a/head/offlineimap/folder/Base.py b/head/offlineimap/folder/Base.py
index f80c78f..9f39848 100644
--- a/head/offlineimap/folder/Base.py
+++ b/head/offlineimap/folder/Base.py
@@ -32,3 +32,24 @@ class BaseFolder:
     def getfullname(self):
         return self.getroot() + self.getsep() + self.getname()
     
+    def isuidvalidityok(self, remotefolder):
+        raise NotImplementedException
+
+    def getuidvalidity(self):
+        raise NotImplementedException
+
+    def saveuidvalidity(self, newval):
+        raise NotImplementedException
+
+    def cachemessagelist(self):
+        """Reads the message list from disk or network and stores it in
+        memory for later use.  This list will not be re-read from disk or
+        memory unless this function is called again."""
+        raise NotImplementedException
+
+    def getmessagelist(self):
+        """Gets the current message list.  If cachemessagelist has not yet
+        been called, it will be called."""
+        raise NotImplementedException
+
+    
diff --git a/head/offlineimap/folder/Maildir.py b/head/offlineimap/folder/Maildir.py
index ada77d6..46b5b47 100644
--- a/head/offlineimap/folder/Maildir.py
+++ b/head/offlineimap/folder/Maildir.py
@@ -18,11 +18,64 @@
 
 from Base import BaseFolder
 from imapsync import imaputil
+import os.path, os, re
 
 class MaildirFolder(BaseFolder):
     def __init__(self, root, name):
         self.name = name
         self.root = root
         self.sep = '.'
+        self.uidfilename = os.path.join(self.getfullname(), "imapsync.uidvalidity")
+        self.messagelist = None
+
+    def getuidvalidity(self):
+        if not os.path.exists(self.uidfilename):
+            return None
+        file = open(self.uidfilename, "rt")
+        retval = int(file.readline().strip())
+        file.close()
+        return retval
+
+    def saveuidvalidity(self, newval):
+        file = open(self.uidfilename, "wt")
+        file.write("%d\n", newval)
+        file.close()
+
+    def isuidvalidityok(self, remotefolder):
+        myval = self.getuidvalidity()
+        if myval != None:
+            return myval == remotefolder.getuidvalidity()
+        else:
+            self.saveuidvalidity(remotefolder.getuidvalidity())
+            
+    def cachemessagelist(self):
+        """Cache the message list.  Maildir flags are:
+        R (replied)
+        S (seen)
+        T (trashed)
+        D (draft)
+        F (flagged)
+        and must occur in ASCII order."""
+        self.messagelist = {}
+        files = []
+        for dirannex in ['new', 'cur']:
+            fulldirname = os.path.join(self.getfullname(), dirannex)
+            files.append([os.path.join(fulldirname, filename) for
+                          filename in os.listdir(fulldirname)])
+        for file in files:
+            messagename = os.path.basename(file)
+            uid = int(re.search(',U=(\d+)', messagename).group(1))
+            flagmatch = re.search(':.*2,([A-Z]+)')
+            flags = []
+            if flagmatch:
+                flags = [f for x in flagmatch.group(1)]
+            self.messagelist[uid] = {'uid': uid,
+                                     'flags': flags,
+                                     'filename': messagename}
+            
+    def getmessagelist(self):
+        if self.messagelist == None:
+            self.cachemessagelist()
+        return self.messagelist