diff --git a/mozilla/mailnews/base/public/msgCore.h b/mozilla/mailnews/base/public/msgCore.h
index 728837a411e..39e1f3ce02d 100644
--- a/mozilla/mailnews/base/public/msgCore.h
+++ b/mozilla/mailnews/base/public/msgCore.h
@@ -158,6 +158,8 @@ NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_MAILNEWS, value)
              conflict, I reserve values between 12500 and 12999 for it.
 */
 #define NS_MSG_CUSTOM_HEADERS_OVERFLOW NS_MSG_GENERATE_FAILURE(28) //when num of custom headers exceeds 50
+#define NS_MSG_INVALID_CUSTOM_HEADER NS_MSG_GENERATE_FAILURE(29) //when custom header has invalid characters (as per rfc 2822) 
+
 #define NS_MSGCOMP_ERROR_BEGIN	12500
 /* NS_ERROR_NNTP_NO_CROSS_POSTING lives here, and not in nsMsgComposeStringBundle.h, because it is used in news and compose. */
 #define NS_ERROR_NNTP_NO_CROSS_POSTING NS_MSG_GENERATE_FAILURE(12554)
diff --git a/mozilla/mailnews/base/resources/content/mailWidgets.xml b/mozilla/mailnews/base/resources/content/mailWidgets.xml
index e3a3c18b7f3..f38b425159f 100644
--- a/mozilla/mailnews/base/resources/content/mailWidgets.xml
+++ b/mozilla/mailnews/base/resources/content/mailWidgets.xml
@@ -422,7 +422,13 @@
             }
             var hdrsArray = new Array;
             if (hdrs)
-              hdrsArray = hdrs.split(": ");
+            {
+              hdrs = hdrs.replace(/\s+/g,'');  //remove white spaces before splitting 
+              hdrsArray = hdrs.split(":");
+              for (var i = 0; i< hdrsArray.length; i++) 
+                if (!hdrsArray[i])
+                   hdrsArray.splice(i,1);  //remove any null elements
+            }
             var bundle = this.stringBundle;
             var j=0;
             for (var i=0; i<ids.length; i++)
diff --git a/mozilla/mailnews/base/search/resources/content/CustomHeaders.js b/mozilla/mailnews/base/search/resources/content/CustomHeaders.js
index 3e6b7557d3e..6774ddc2c3f 100644
--- a/mozilla/mailnews/base/search/resources/content/CustomHeaders.js
+++ b/mozilla/mailnews/base/search/resources/content/CustomHeaders.js
@@ -65,7 +65,11 @@ function initializeDialog(hdrs)
 {
   if (hdrs)
   {
-    gArrayHdrs = hdrs.split(": ");
+    hdrs = hdrs.replace(/\s+/g,'');  //remove white spaces before splitting
+    gArrayHdrs = hdrs.split(":");
+    for (var i = 0; i< gArrayHdrs.length; i++) 
+      if (!gArrayHdrs[i])
+        gArrayHdrs.splice(i,1);  //remove any null elements
     initializeRows();
   }
 }
@@ -101,7 +105,11 @@ function onOk()
 {  
   if (gArrayHdrs.length)
   {
-    var hdrs = gArrayHdrs.join(": ");
+    var hdrs;
+    if (gArrayHdrs.length == 1)
+      hdrs = gArrayHdrs;
+    else
+      hdrs = gArrayHdrs.join(": ");
     gPrefs.setCharPref("mailnews.customHeaders", hdrs);
     // flush prefs to disk, in case we crash, to avoid dataloss and problems with filters that use the custom headers
     var prefService = Components.classes["@mozilla.org/preferences-service;1"].getService(Components.interfaces.nsIPrefService);
diff --git a/mozilla/mailnews/base/search/resources/locale/en-US/filter.properties b/mozilla/mailnews/base/search/resources/locale/en-US/filter.properties
index a3d6410dcb2..e95dfb5a67b 100644
--- a/mozilla/mailnews/base/search/resources/locale/en-US/filter.properties
+++ b/mozilla/mailnews/base/search/resources/locale/en-US/filter.properties
@@ -12,3 +12,4 @@ untitledFilterName=untitled filter
 filterListBackUpMsg=Your filters do not work because the rules.dat file, which contains your filters, could not be read. A new rules.dat file will be created and a backup of the old file, called rulesbackup.dat, will be created in the same directory.
 customHeaderOverflow=You've exceeded the limit of 50 custom headers. Please remove one or more custom headers and try again.
 filterCustomHeaderOverflow=Your filters have exceeded the limit of 50 custom headers. Please edit the rules.dat file, which contains your filters, to use fewer custom headers.
+invalidCustomHeader=One of your filters uses a custom header that contains an invalid character, such as ':', a non-printable character, a non-ascii character, or an eight-bit ascii character. Please edit the rules.dat file, which contains your filters, to remove invalid characters from your custom headers.
diff --git a/mozilla/mailnews/base/search/src/nsMsgFilterService.cpp b/mozilla/mailnews/base/search/src/nsMsgFilterService.cpp
index eaaaf677a0a..fa9663c7530 100644
--- a/mozilla/mailnews/base/search/src/nsMsgFilterService.cpp
+++ b/mozilla/mailnews/base/search/src/nsMsgFilterService.cpp
@@ -111,6 +111,8 @@ NS_IMETHODIMP nsMsgFilterService::OpenFilterList(nsIFileSpec *filterFile, nsIMsg
     }
     else if(ret == NS_MSG_CUSTOM_HEADERS_OVERFLOW && aMsgWindow)
       ThrowAlertMsg("filterCustomHeaderOverflow", aMsgWindow);
+    else if(ret == NS_MSG_INVALID_CUSTOM_HEADER && aMsgWindow)
+      ThrowAlertMsg("invalidCustomHeader", aMsgWindow);
   }
 	return ret;
 }
diff --git a/mozilla/mailnews/base/search/src/nsMsgSearchAdapter.cpp b/mozilla/mailnews/base/search/src/nsMsgSearchAdapter.cpp
index c8f543d0179..220816f9c91 100644
--- a/mozilla/mailnews/base/search/src/nsMsgSearchAdapter.cpp
+++ b/mozilla/mailnews/base/search/src/nsMsgSearchAdapter.cpp
@@ -1112,19 +1112,27 @@ nsMsgSearchValidityManager::SetOtherHeadersInTable (nsIMsgSearchValidityTable *a
 {
   PRUint32 customHeadersLength = strlen(customHeaders);
   PRUint32 numHeaders=0;
-  PRUint32 i=0;
   if (customHeadersLength)
   {
-    for (i=0;i <customHeadersLength; i++)
-      if (customHeaders[i] == ':')
-        numHeaders++;
-    numHeaders++;
+    char *headersString = nsCRT::strdup(customHeaders);
+
+    nsCAutoString hdrStr;
+    hdrStr.Adopt(headersString);
+    hdrStr.StripWhitespace();  //remove whitespace before parsing
+
+    char *newStr=nsnull;
+    char *token = nsCRT::strtok(headersString,":", &newStr);
+    while(token)
+    {
+      numHeaders++;
+      token = nsCRT::strtok(newStr,":", &newStr);
+    }
   }
 
   NS_ASSERTION(nsMsgSearchAttrib::OtherHeader + numHeaders < nsMsgSearchAttrib::kNumMsgSearchAttributes, "more headers than the table can hold");
 
   PRUint32 maxHdrs= PR_MIN(nsMsgSearchAttrib::OtherHeader + numHeaders+1, nsMsgSearchAttrib::kNumMsgSearchAttributes);
-  for (i=nsMsgSearchAttrib::OtherHeader+1;i< maxHdrs;i++)
+  for (PRUint32 i=nsMsgSearchAttrib::OtherHeader+1;i< maxHdrs;i++)
   {
     aTable->SetAvailable (i, nsMsgSearchOp::Contains, 1);   // added for arbitrary headers
     aTable->SetEnabled   (i, nsMsgSearchOp::Contains, 1); 
diff --git a/mozilla/mailnews/base/search/src/nsMsgSearchTerm.cpp b/mozilla/mailnews/base/search/src/nsMsgSearchTerm.cpp
index 166afbba44b..78d03ec5a30 100644
--- a/mozilla/mailnews/base/search/src/nsMsgSearchTerm.cpp
+++ b/mozilla/mailnews/base/search/src/nsMsgSearchTerm.cpp
@@ -108,6 +108,10 @@ nsresult NS_MsgGetAttributeFromString(const char *string, PRInt16 *attrib)
 	if (!found)
   {
     nsresult rv;
+    PRBool goodHdr;
+    IsRFC822HeaderFieldName(string, &goodHdr);
+    if (!goodHdr)
+      return NS_MSG_INVALID_CUSTOM_HEADER;
     //49 is for showing customize... in ui, headers start from 50 onwards up until 99.
     *attrib = nsMsgSearchAttrib::OtherHeader+1;
 
@@ -124,32 +128,33 @@ nsresult NS_MsgGetAttributeFromString(const char *string, PRInt16 *attrib)
     if (!headers.IsEmpty())
     {
       char *headersString = ToNewCString(headers);
+
+      nsCAutoString hdrStr;
+      hdrStr.Adopt(headersString);
+      hdrStr.StripWhitespace();  //remove whitespace before parsing
+
       char *newStr=nsnull;
-      char *token = nsCRT::strtok(headersString,": ", &newStr);
+      char *token = nsCRT::strtok(headersString,":", &newStr);
       PRUint32 i=0;
       while (token)
       {
         if (nsCRT::strcasecmp(token, string) == 0)
         {
-          *attrib += i; 
-          nsMemory::Free(headersString); //we found custom header in the pref
+          *attrib += i; //we found custom header in the pref
           return NS_OK;
         }
-        token = nsCRT::strtok(newStr,": ", &newStr);
+        token = nsCRT::strtok(newStr,":", &newStr);
         i++;
 
         //we know we can have a max of 50 custom headers
         if ( nsMsgSearchAttrib::OtherHeader + i >= nsMsgSearchAttrib::kNumMsgSearchAttributes -1)
         {
-           nsMemory::Free(headersString);
            NS_ASSERTION(0, "pref has more headers than the table can hold");
            return NS_MSG_CUSTOM_HEADERS_OVERFLOW;
         }
       }
 
       *attrib += i; //this is *attrib for the new custom header 
-
-      nsMemory::Free(headersString);
       headers.Append(": "); //Adding additonal header to the pref so append the separator
     }