diff --git a/mozilla/mailnews/imap/src/nsImapProtocol.cpp b/mozilla/mailnews/imap/src/nsImapProtocol.cpp
index 44ca0218053..0d36b9a0749 100644
--- a/mozilla/mailnews/imap/src/nsImapProtocol.cpp
+++ b/mozilla/mailnews/imap/src/nsImapProtocol.cpp
@@ -317,6 +317,7 @@ static PRBool gUseLiteralPlus = PR_TRUE;
 static PRBool gExpungeAfterDelete = PR_FALSE;
 static PRBool gCheckDeletedBeforeExpunge = PR_FALSE; //bug 235004
 static PRInt32 gResponseTimeout = 60;
+static nsCStringArray gCustomDBHeaders;
 
 nsresult nsImapProtocol::GlobalInitialization()
 {
@@ -342,6 +343,9 @@ nsresult nsImapProtocol::GlobalInitialization()
     prefBranch->GetBoolPref("mail.imap.expunge_after_delete", &gExpungeAfterDelete);
     prefBranch->GetBoolPref("mail.imap.check_deleted_before_expunge", &gCheckDeletedBeforeExpunge);
     prefBranch->GetIntPref("mailnews.tcptimeout", &gResponseTimeout);
+    nsXPIDLCString customDBHeaders;
+    prefBranch->GetCharPref("mailnews.customDBHeaders", getter_Copies(customDBHeaders));
+    gCustomDBHeaders.ParseString(customDBHeaders, ", ");
     return NS_OK;
 }
 
@@ -3019,6 +3023,15 @@ nsImapProtocol::FetchMessage(const char * messageIds,
         const char *dbHeaders = (gUseEnvelopeCmd) ? IMAP_DB_HEADERS : IMAP_ENV_AND_DB_HEADERS;
         nsXPIDLCString arbitraryHeaders;
         GetArbitraryHeadersToDownload(getter_Copies(arbitraryHeaders));
+        for (PRInt32 i = 0; i < gCustomDBHeaders.Count(); i++)
+        {
+          if (arbitraryHeaders.Find(* (gCustomDBHeaders[i]), PR_TRUE) == kNotFound)
+          {
+            if (!arbitraryHeaders.IsEmpty())
+              arbitraryHeaders.Append(' ');
+            arbitraryHeaders.Append(gCustomDBHeaders[i]->get());
+          }
+        }   
         if (arbitraryHeaders.IsEmpty())
           headersToDL = nsCRT::strdup(dbHeaders);
         else
diff --git a/mozilla/mailnews/local/src/nsParseMailbox.cpp b/mozilla/mailnews/local/src/nsParseMailbox.cpp
index d0923baa0f8..fef93c2af2c 100644
--- a/mozilla/mailnews/local/src/nsParseMailbox.cpp
+++ b/mozilla/mailnews/local/src/nsParseMailbox.cpp
@@ -475,6 +475,28 @@ nsParseMailMessageState::nsParseMailMessageState()
   m_position = 0;
   m_IgnoreXMozillaStatus = PR_FALSE;
   m_state = nsIMsgParseMailMsgState::ParseBodyState;
+
+  // setup handling of custom db headers, headers that are added to .msf files
+  // as properties of the nsMsgHdr objects, controlled by the 
+  // pref mailnews.customDBHeaders.
+  // E.g., if mailnews.customDBHeaders is "X-Spam-Score", and we're parsing
+  // a mail message with the X-Spam-Score header, we'll set the 
+  // "x-spam-score" property of nsMsgHdr to the value of the header.
+  m_customDBHeaderValues = nsnull;
+  nsXPIDLCString customDBHeaders;
+  nsCOMPtr<nsIPrefBranch> pPrefBranch(do_GetService(NS_PREFSERVICE_CONTRACTID));
+  if (pPrefBranch)
+  {
+     pPrefBranch->GetCharPref("mailnews.customDBHeaders",  getter_Copies(customDBHeaders));
+     ToLowerCase(customDBHeaders);
+     m_customDBHeaders.ParseString(customDBHeaders, ", ");
+     if (m_customDBHeaders.Count())
+     {
+       m_customDBHeaderValues = new struct message_header [m_customDBHeaders.Count()];
+       if (!m_customDBHeaderValues)
+         m_customDBHeaders.Clear();
+     }
+  }
   Clear();
 
   m_HeaderAddressParser = do_GetService(NS_MAILNEWS_MIME_HEADER_PARSER_CONTRACTID);
@@ -484,6 +506,7 @@ nsParseMailMessageState::~nsParseMailMessageState()
 {
   ClearAggregateHeader (m_toList);
   ClearAggregateHeader (m_ccList);
+  delete [] m_customDBHeaderValues;
 }
 
 void nsParseMailMessageState::Init(PRUint32 fileposition)
@@ -524,6 +547,9 @@ NS_IMETHODIMP nsParseMailMessageState::Clear()
   m_headers.ResetWritePos();
   m_envelope.ResetWritePos();
   m_receivedTime = LL_ZERO;
+  for (PRInt32 i = 0; i < m_customDBHeaders.Count(); i++)
+    m_customDBHeaderValues[i].length = 0;
+
   return NS_OK;
 }
 
@@ -946,6 +972,15 @@ int nsParseMailMessageState::ParseHeaders ()
         header = &m_keywords;
       break;
     }
+    if (!header && m_customDBHeaders.Count())
+    {
+      nsDependentCSubstring headerStr(buf, end);
+
+      ToLowerCase(headerStr);
+      PRInt32 customHeaderIndex = m_customDBHeaders.IndexOf(headerStr);
+      if (customHeaderIndex != kNotFound)
+        header = & m_customDBHeaderValues[customHeaderIndex];
+    }
     
     buf = colon + 1;
     while (*buf == ' ' || *buf == '\t')
@@ -954,6 +989,9 @@ int nsParseMailMessageState::ParseHeaders ()
     value = buf;
     if (header)
       header->value = value;
+    else
+    {
+    }
     
 SEARCH_NEWLINE:
     while (*buf != 0 && *buf != nsCRT::CR && *buf != nsCRT::LF)
@@ -1425,6 +1463,11 @@ int nsParseMailMessageState::FinalizeHeaders()
           m_newMsgHdr->SetPriority(nsMsgPriority::none);
         if (keywords)
           m_newMsgHdr->SetStringProperty("keywords", keywords->value);
+        for (PRInt32 i = 0; i < m_customDBHeaders.Count(); i++)
+        {
+          if (m_customDBHeaderValues[i].length)
+            m_newMsgHdr->SetStringProperty((m_customDBHeaders[i])->get(), m_customDBHeaderValues[i].value);
+        }
         if (content_type)
         {
           char *substring = PL_strstr(content_type->value, "charset");
diff --git a/mozilla/mailnews/local/src/nsParseMailbox.h b/mozilla/mailnews/local/src/nsParseMailbox.h
index 960a5a72aa9..7b45e0bf700 100644
--- a/mozilla/mailnews/local/src/nsParseMailbox.h
+++ b/mozilla/mailnews/local/src/nsParseMailbox.h
@@ -148,9 +148,15 @@ public:
   struct message_header m_mdn_dnt; /* MDN Disposition-Notification-To: header */
 
   PRTime m_receivedTime;
-  PRUint16			m_body_lines;
+  PRUint16              m_body_lines;
   
-  PRBool			m_IgnoreXMozillaStatus;
+  PRBool                m_IgnoreXMozillaStatus;
+
+  // this enables extensions to add the values of particular headers to 
+  // the .msf file as properties of nsIMsgHdr. It is initialized from a
+  // pref, mailnews.customDBHeaders
+  nsCStringArray        m_customDBHeaders;
+  struct message_header *m_customDBHeaderValues;
 protected:
   nsCOMPtr<nsIMsgStringService> mStringService;
 
diff --git a/mozilla/mailnews/mailnews.js b/mozilla/mailnews/mailnews.js
index 3620403628e..df3bc6c8b0f 100644
--- a/mozilla/mailnews/mailnews.js
+++ b/mozilla/mailnews/mailnews.js
@@ -368,6 +368,8 @@ pref("ldap_2.prefs_migrated",      false);
 
 pref("mailnews.confirm.moveFoldersToTrash", true);
 
+pref("mailnews.customDBHeaders", "");
+
 pref("mailnews.reuse_message_window", true);
 pref("mailnews.reuse_thread_window2", false);
 pref("mailnews.open_window_warning", 10); // warn user if they attempt to open more than this many messages at once