diff -udpr mutt-1.2.5.orig/OPS mutt-1.2.5.edit_threads/OPS
--- mutt-1.2.5.orig/OPS	Tue Feb 15 16:28:466 2000
+++ mutt-1.2.5.edit_threads/OPS	Sat Sep  1 15:28:03 2001
@@ -87,6 +87,7 @@ OP_LAST_ENTRY "move to the last entry"
 OP_LIST_REPLY "reply to specified mailing list"
 OP_MACRO "execute a macro"
 OP_MAIL "compose a new mail message"
+OP_MAIN_BREAK_THREAD "break the thread in two"
 OP_MAIN_CHANGE_FOLDER "open a different folder"
 OP_MAIN_CHANGE_FOLDER_READONLY "open a different folder in read only mode"
 OP_MAIN_CLEAR_FLAG "clear a status flag from a message"
@@ -95,6 +96,7 @@ OP_MAIN_FETCH_MAIL "retrieve mail from P
 OP_MAIN_FIRST_MESSAGE "move to the first message"
 OP_MAIN_LAST_MESSAGE "move to the last message"
 OP_MAIN_LIMIT "show only messages matching a pattern"
+OP_MAIN_LINK_THREADS "link tagged messages to the current one"
 OP_MAIN_NEXT_NEW "jump to the next new message"
 OP_MAIN_NEXT_SUBTHREAD "jump to the next subthread"
 OP_MAIN_NEXT_THREAD "jump to the next thread"
diff -udpr mutt-1.2.5.orig/copy.c mutt-1.2.5.edit_threads/copy.c
--- mutt-1.2.5.orig/copy.c	Thu Jun 15 23:066:40 2000
+++ mutt-1.2.5.edit_threads/copy.c	Sun Sep  2 15:06:28 2001
@@ -92,6 +92,9 @@ mutt_copy_hdr (FILE *in, FILE *out, long
 	    (mutt_strncasecmp ("Content-Length:", buf, 15) == 0 ||
 	     mutt_strncasecmp ("Lines:", buf, 6) == 0))
 	  continue;
+	if ((flags & CH_UPDATE_THREADS) &&
+	    mutt_strncasecmp ("X-Thread-as-Reply-To:", buf, 21) == 0)
+	  continue;
 	ignore = 0;
       }
 
@@ -168,6 +171,9 @@ mutt_copy_hdr (FILE *in, FILE *out, long
 	     mutt_strncasecmp ("type:", buf + 8, 5) == 0)) ||
 	   mutt_strncasecmp ("mime-version:", buf, 13) == 0))
 	continue;
+      if ((flags & CH_UPDATE_THREADS) &&
+	  mutt_strncasecmp ("X-Thread-as-Reply-To:", buf, 21) == 0)
+	continue;
 
       /* Find x -- the array entry where this header is to be saved */
       if (flags & CH_REORDER)
@@ -276,6 +282,7 @@ mutt_copy_hdr (FILE *in, FILE *out, long
  	CH_UPDATE_LEN	write new Content-Length: and Lines:
  	CH_XMIT		ignore Lines: and Content-Length:
  	CH_WEED		do header weeding
+	CH_UPDATE_THREADS update the X-Thread-as-Reply-To: header
 
    prefix
    	string to use if CH_PREFIX is set
@@ -286,6 +293,8 @@ mutt_copy_header (FILE *in, HEADER *h, F
 {
   char buffer[SHORT_STRING];
 
+  flags |= (h->threads_changed ? CH_UPDATE_THREADS : 0);
+
   if (mutt_copy_hdr (in, out, h->offset, h->content->offset, flags, prefix) == -1)
     return (-1);
 
@@ -307,6 +316,26 @@ mutt_copy_header (FILE *in, HEADER *h, F
   {
     if ((flags & CH_NOSTATUS) == 0)
     {
+      if (h->threads_changed)
+      {
+	if  (h->env->references)
+	{
+	  if (fputs ("X-Thread-as-Reply-To: ", out) == EOF)
+	  return (-1);
+
+	  if (fputs (h->env->references->data, out) == EOF)
+	  return (-1);
+
+	  if (fputc ('\n', out) == EOF)
+	    return (-1);
+	}
+	else
+	{
+	  if (fputs ("X-Thread-as-Reply-To: <>\n", out) == EOF)
+	    return (-1);
+	}
+      }
+
       if (h->old || h->read)
       {
 	if (fputs ("Status: ", out) == EOF)
diff -udpr mutt-1.2.5.orig/curs_main.c mutt-1.2.5.edit_threads/curs_main.c
--- mutt-1.2.5.orig/curs_main.c	Tue Jul 25  10:02:26 2000
+++ mutt-1.2.5.edit_threads/curs_main.c	Sun Sep  2 15:09:38 2001
@@ -915,6 +915,102 @@ int mutt_index_menu (void)
 	  menu->redraw = REDRAW_INDEX | REDRAW_STATUS;
 	break;
 
+      case OP_MAIN_BREAK_THREAD:
+
+	CHECK_MSGCOUNT;
+	CHECK_READONLY;
+
+        if ((Sort & SORT_MASK) != SORT_THREADS)
+        {
+	  mutt_error _("Threading is not enabled.");
+	  break;
+	}
+
+        if (CURHDR->parent == NULL)
+        {
+	  mutt_error _("No thread to break.");
+	  break;
+	}
+
+	if (CURHDR->env->old_references == NULL && CURHDR->changed == 0) {
+	  CURHDR->env->old_references = CURHDR->env->references;
+	  CURHDR->env->references = NULL;
+	}
+	else
+	  mutt_free_list (&CURHDR->env->references);
+	CURHDR->threads_changed = CURHDR->changed = 1;
+	Context->changed = 1;
+
+	{ 
+	  HEADER *oldcur = CURHDR;	
+	  mutt_break_thread (Context, CURHDR);
+	  mutt_sort_threads (Context, 0);
+	  mutt_adjust_virtual (Context);
+	  menu->current = oldcur->virtual; 
+	}
+	mutt_message _("Thread broken");
+	menu->redraw |= REDRAW_STATUS | REDRAW_INDEX | REDRAW_MOTION;
+	break;
+
+      case OP_MAIN_LINK_THREADS:
+
+	CHECK_MSGCOUNT;
+	CHECK_READONLY;
+
+        if ((Sort & SORT_MASK) != SORT_THREADS)
+        {
+	  mutt_error _("Threading is not enabled.");
+	  break;
+	}
+
+	if (!CURHDR->env->message_id)
+	  mutt_error _("No Message-ID: header available to link thread");
+	else
+	{
+	  int changed = 0;
+	  HEADER *oldcur = CURHDR;	
+
+	  for (i = 0; i < Context->vcount; i++)
+	  {
+	    HEADER *hdr = Context->hdrs[Context->v2r[i]];
+
+	    if (i != menu->current && hdr->tagged)
+	    {
+	      LIST *tmp = mutt_new_list ();
+	      
+	      tmp->data = safe_strdup (oldcur->env->message_id);;
+	      tmp->next = NULL;
+
+	      if (hdr->env->old_references == NULL && hdr->changed == 0) {
+		hdr->env->old_references = hdr->env->references;
+	      }
+	      hdr->env->references = tmp;
+
+	      mutt_set_flag (Context, hdr, M_TAG, 0);
+	      mutt_link_thread (Context, oldcur, hdr);
+	
+	      hdr->threads_changed = hdr->changed = 1;
+	      changed = 1;
+	    }
+	  }
+
+	  if (changed)
+	  {
+	    Context->changed = 1;
+
+	    mutt_sort_threads (Context, 0);
+	    mutt_adjust_virtual (Context);
+	    mutt_message _("Threads linked");
+	    menu->redraw |= REDRAW_STATUS | REDRAW_INDEX | REDRAW_MOTION;
+
+	    menu->current = oldcur->virtual; 
+	    break;
+	  }
+	  else
+	    mutt_error _("No thread linked");
+	}
+	break;
+
 	/* --------------------------------------------------------------------
 	 * The following operations can be performed inside of the pager.
 	 */
diff -udpr mutt-1.2.5.orig/doc/manual.sgml.head mutt-1.2.5.edit_threads/doc/manual.sgml.head
--- mutt-1.2.5.orig/doc/manual.sgml.head	Saat Apr 22 11:33:46 2000
+++ mutt-1.2.5.edit_threads/doc/manual.sgml.head	Sat Sep  1 15:29:03 2001
@@ -1952,6 +1952,34 @@ used a threaded news client, this is the
 with large volume mailing lists easier because you can easily delete
 uninteresting threads and quickly find topics of value.
 
+<sect1>Editing threads
+<p>
+Mutt has the ability to dynamically restructure threads that are broken
+either by misconfigured software or bad behaviour from some
+correspondents. This allows to clean your mailboxes from these
+annoyances which make it hard to follow a discussion.
+
+<sect2>Linking threads
+<p>
+
+Some mailers tend to "forget" to correctly set the "In-Reply-To:" and
+"References:" headers when replying to a message. This results in broken
+discussions because Mutt has not enough information to guess the correct
+threading.
+You can fix this by tagging the replies to a mail, then go onto this
+mail and use the ``link-threads'' function (bound to  ``&'' by default).
+The replies will then be connected to the "parent" message.
+
+<sect2>Breaking threads
+<p>
+
+On mailing lists, some people are in the bad habit of starting a new
+discussion by hitting "reply" to any message from the list and changing
+the subject to a totally unrelated one.
+You can fix such threads by using the ``break-thread'' function (bound
+by default to  ``#''), which will turn the subthread starting from the
+current message into a whole different thread.
+
 <sect1>Delivery Status Notification (DSN) Support
 <p>
 RFC1894 defines a set of MIME content types for relaying information
diff -udpr mutt-1.2.5.orig/functions.h mutt-1.2.5.edit_threads/functions.h
--- mutt-1.2.5.orig/functions.h	Fri Mar  3  10:10:08 2000
+++ mutt-1.2.5.edit_threads/functions.h	Sat Sep  1 15:29:03 2001
@@ -66,6 +66,7 @@ struct binding_t OpGeneric[] = {
 struct binding_t OpMain[] = {
   { "create-alias",		OP_CREATE_ALIAS,		"a" },
   { "bounce-message",		OP_BOUNCE_MESSAGE,		"b" },
+  { "break-thread",		OP_MAIN_BREAK_THREAD,		"#" },
   { "change-folder",		OP_MAIN_CHANGE_FOLDER,		"c" },
   { "change-folder-readonly",	OP_MAIN_CHANGE_FOLDER_READONLY,	"\033c" },
   { "collapse-thread",		OP_MAIN_COLLAPSE_THREAD,	"\033v" },
@@ -89,6 +90,7 @@ struct binding_t OpMain[] = {
   { "next-undeleted",		OP_MAIN_NEXT_UNDELETED,		"j" },
   { "previous-undeleted",	OP_MAIN_PREV_UNDELETED,		"k" },
   { "limit",			OP_MAIN_LIMIT,			"l" },
+  { "link-threads",		OP_MAIN_LINK_THREADS,		"&" },
   { "list-reply",		OP_LIST_REPLY,			"L" },
   { "mail",			OP_MAIL,			"m" },
   { "toggle-new",		OP_TOGGLE_NEW,			"N" },
diff -udpr mutt-1.2.5.orig/headers.c mutt-1.2.5.edit_threads/headers.c
--- mutt-1.2.5.orig/headers.c	Wed Apr 12 188:31:38 2000
+++ mutt-1.2.5.edit_threads/headers.c	Sun Sep  2 15:15:01 2001
@@ -110,6 +110,8 @@ void mutt_edit_headers (const char *edit
   /* restore old info. */
   n->references = msg->env->references;
   msg->env->references = NULL;
+  n->old_references = msg->env->old_references;
+  msg->env->old_references = NULL;
   mutt_free_envelope (&msg->env);
   msg->env = n;
 
@@ -204,5 +206,8 @@ void mutt_edit_headers (const char *edit
   }
 
   if (!in_reply_to)
+  {
     mutt_free_list (&msg->env->references);
+    mutt_free_list (&msg->env->old_references);
+  }
 }
diff -udpr mutt-1.2.5.orig/mutt.h mutt-1.2.5.edit_threads/mutt.h
--- mutt-1.2.5.orig/mutt.h	Thu Jun  8 12:000:14 2000
+++ mutt-1.2.5.edit_threads/mutt.h	Sun Sep  2 15:20:12 2001
@@ -67,6 +67,7 @@
 #define CH_NOLEN	(1<<12) /* don't write Content-Length: and Lines: */
 #define CH_WEED_DELIVERED (1<<13) /* weed eventual Delivered-To headers */
 #define CH_FORCE_FROM	(1<<14)	/* give CH_FROM precedence over CH_WEED? */
+#define CH_UPDATE_THREADS (1<<15) /* update X-Thread-as-Reply-To: */
 
 /* flags for mutt_enter_string() */
 #define  M_ALIAS   1      /* do alias "completion" by calling up the alias-menu */
@@ -464,6 +465,7 @@ typedef struct envelope
   char *supersedes;
   char *date;
   LIST *references;		/* message references (in reverse order) */
+  LIST *old_references;		/* message references before thread editing */
   LIST *userhdrs;		/* user defined headers */
 } ENVELOPE;
 
@@ -562,6 +564,7 @@ typedef struct header
   unsigned int display_subject : 1; /* used for threading */
   unsigned int fake_thread : 1;     /* no ref matched, but subject did */
   unsigned int threaded : 1;        /* message has been threaded */
+  unsigned int threads_changed : 1; /* threads have been broken/linked */
   unsigned int recip_valid : 1;  /* is_recipient is valid */
   unsigned int active : 1;	    /* message is not to be removed */
   
diff -udpr mutt-1.2.5.orig/muttlib.c mutt-1.2.5.edit_threads/muttlib.c
--- mutt-1.2.5.orig/muttlib.c	Fri Jul  7 011:06:16 2000
+++ mutt-1.2.5.edit_threads/muttlib.c	Sun Sep  2 15:15:20 2001
@@ -564,6 +564,7 @@ void mutt_free_envelope (ENVELOPE **p)
   safe_free ((void **) &(*p)->supersedes);
   safe_free ((void **) &(*p)->date);
   mutt_free_list (&(*p)->references);
+  mutt_free_list (&(*p)->old_references);
   mutt_free_list (&(*p)->userhdrs);
   safe_free ((void **) p);
 }
diff -udpr mutt-1.2.5.orig/parse.c mutt-1.2.5.edit_threads/parse.c
--- mutt-1.2.5.orig/parse.c	Sat Apr 22 10:449:30 2000
+++ mutt-1.2.5.edit_threads/parse.c	Sun Sep  2 15:50:51 2001
@@ -875,11 +875,13 @@ ENVELOPE *mutt_read_rfc822_header (FILE 
   char *line = safe_malloc (LONG_STRING);
   char *p;
   char in_reply_to[STRING];
+  char thread_as_reply_to[STRING];
   long loc;
   int matched;
   size_t linelen = LONG_STRING;
 
   in_reply_to[0] = 0;
+  thread_as_reply_to[0] = 0;
 
   if (hdr)
   {
@@ -1181,6 +1183,13 @@ ENVELOPE *mutt_read_rfc822_header (FILE 
 	  }
 	  matched = 1;
 	}
+	else if (mutt_strcasecmp (line + 1, "-thread-as-reply-to") == 0)
+	{
+	  strfcpy (thread_as_reply_to, p, sizeof (thread_as_reply_to));
+	  rfc2047_decode (thread_as_reply_to, thread_as_reply_to,
+			  sizeof (thread_as_reply_to));
+	}
+	break;
 	    
       default:
 	break;
@@ -1231,6 +1240,21 @@ ENVELOPE *mutt_read_rfc822_header (FILE 
       }
       else
 	safe_free ((void **) &p);
+    }
+
+    if (thread_as_reply_to[0]) 
+    {
+      e->old_references = e->references;
+      e->references = NULL;
+      if (mutt_strcmp (thread_as_reply_to, "<>") != 0 &&
+	  (p = extract_message_id (thread_as_reply_to)) != NULL)
+      {
+	LIST *tmp = mutt_new_list ();
+
+	tmp->data = p;
+	tmp->next = NULL;
+	e->references = tmp;
+      }
     }
 
     /* do RFC2047 decoding */
diff -udpr mutt-1.2.5.orig/protos.h mutt-1.2.5.edit_threads/protos.h
--- mutt-1.2.5.orig/protos.h	Tue May 16 17::23:12 2000
+++ mutt-1.2.5.edit_threads/protos.h	Sun Sep  2 15:25:53 2001
@@ -126,12 +126,14 @@ char *mutt_make_date (char *, size_t);
 
 const char *mutt_fqdn(short);
 
+void mutt_adjust_virtual (CONTEXT *);
 void mutt_adv_mktemp (char *, size_t);
 void mutt_alias_menu (char *, size_t, ALIAS *);
 void mutt_block_signals (void);
 void mutt_block_signals_system (void);
 void mutt_body_handler (BODY *, STATE *);
 void mutt_bounce_message (FILE *fp, HEADER *, ADDRESS *);
+void mutt_break_thread (CONTEXT *, HEADER *);
 void mutt_buffy (char *);
 void mutt_check_rescore (CONTEXT *);
 void mutt_clear_error (void);
@@ -163,6 +165,7 @@ void mutt_free_parameter (PARAMETER **);
 void mutt_generate_header (char *, size_t, HEADER *, int);
 void mutt_help (int);
 void mutt_linearize_tree (CONTEXT *, int);
+void mutt_link_thread (CONTEXT *, HEADER *, HEADER *);
 void mutt_make_attribution (CONTEXT *ctx, HEADER *cur, FILE *out);
 void mutt_make_forward_subject (ENVELOPE *env, CONTEXT *ctx, HEADER *cur);
 void mutt_make_help (char *, size_t, char *, int, int);
diff -udpr mutt-1.2.5.orig/send.c mutt-1.2.5.edit_threads/send.c
--- mutt-1.2.5.orig/send.c	Mon Mar 13 22:366:56 2000
+++ mutt-1.2.5.edit_threads/send.c	Sun Sep  2 15:16:29 2001
@@ -525,7 +525,10 @@ LIST *mutt_make_references(ENVELOPE *e)
 {
   LIST *t, *l;
   
-  l = mutt_copy_list(e->references);
+  if (e->old_references)
+    l = mutt_copy_list(e->old_references);
+  else
+    l = mutt_copy_list(e->references);
   
   if(e->message_id)
   {
diff -udpr mutt-1.2.5.orig/sendlib.c mutt-1.2.5.edit_threads/sendlib.c
--- mutt-1.2.5.orig/sendlib.c	Sat May 20 088:39:00 2000
+++ mutt-1.2.5.edit_threads/sendlib.c	Sun Sep  2 15:29:41 2001
@@ -1345,10 +1345,13 @@ int mutt_write_rfc822_header (FILE *fp, 
 
   if (mode <= 0)
   {
-    if (env->references)
+    if (env->references || env->old_references)
     {
       fputs ("References:", fp);
-      write_references (env->references, ffp);
+      if (env->old_references)
+	write_references (env->old_references, fp);
+      else
+	write_references (env->references, fp);
       fputc('\n', fp);
     }
 
diff -udpr mutt-1.2.5.orig/sort.c mutt-1.2.5.edit_threads/sort.c
--- mutt-1.2.5.orig/sort.c	Wed Mar 22 08:244:46 2000
+++ mutt-1.2.5.edit_threads/sort.c	Sun Sep  2 15:06:47 2001
@@ -174,6 +174,24 @@ sort_t *mutt_get_sort_func (int method)
   /* not reached */
 }
 
+void mutt_adjust_virtual(CONTEXT *ctx)
+{
+  int i;
+  
+  ctx->vcount = 0;
+  for (i = 0; i < ctx->msgcount; i++)
+  {
+    HEADER *cur = ctx->hdrs[i];
+    if (cur->virtual != -1 || (cur->collapsed && (!ctx->pattern || cur->limited)))
+    {
+      cur->virtual = ctx->vcount;
+      ctx->v2r[ctx->vcount] = i;
+      ctx->vcount++;
+    }
+    cur->msgno = i;
+  }
+}
+
 void mutt_sort_headers (CONTEXT *ctx, int init)
 {
   int i;
@@ -237,18 +255,7 @@ void mutt_sort_headers (CONTEXT *ctx, in
     qsort ((void *) ctx->hdrs, ctx->msgcount, sizeof (HEADER *), sortfunc);
 
   /* adjust the virtual message numbers */
-  ctx->vcount = 0;
-  for (i = 0; i < ctx->msgcount; i++)
-  {
-    HEADER *cur = ctx->hdrs[i];
-    if (cur->virtual != -1 || (cur->collappsed && (!ctx->pattern || cur->limited)))
-    {
-      cur->virtual = ctx->vcount;
-      ctx->v2r[ctx->vcount] = i;
-      ctx->vcount++;
-    }
-    cur->msgno = i;
-  }
+  mutt_adjust_virtual(ctx);
 
   /* re-collapse threads marked as collapsed */
   if ((Sort & SORT_MASK) == SORT_THREADS)
diff -udpr mutt-1.2.5.orig/thread.c mutt-1.2.5.edit_threads/thread.c
--- mutt-1.2.5.orig/thread.c	Sat Apr 22 11::27:08 2000
+++ mutt-1.2.5.edit_threads/thread.c	Sun Sep  2 15:06:47 2001
@@ -888,3 +888,19 @@ int _mutt_traverse_thread (CONTEXT *ctx,
 #undef CHECK_LIMIT
 }
 
+void mutt_break_thread (CONTEXT *ctx, HEADER *cur)
+{
+  unlink_message (&cur->parent->child, cur);
+  cur->parent = NULL;
+  insert_message (&ctx->tree, cur, mutt_get_sort_func (SortAux));
+}
+
+void mutt_link_thread (CONTEXT *ctx, HEADER *cur, HEADER *newchild)
+{
+  if (newchild->parent)
+    unlink_message (&newchild->parent->child, newchild);
+  else
+    unlink_message (&ctx->tree, newchild);
+  newchild->parent = cur;
+  insert_message (&cur->child, newchild, mutt_get_sort_func (SortAux));
+}