Trash folder patch from http://cedricduval.free.fr/mutt/patches/#trash

mutt-trashfolder.diff

diff -urN mutt-1.5.24/PATCHES mutt-1.5.24.new/PATCHES
--- mutt-1.5.24/PATCHES	2015-08-30 19:06:38.000000000 +0200
+++ mutt-1.5.24.new/PATCHES	2015-12-23 22:50:08.000000000 +0100
@@ -0,0 +1 @@
+patch-1.5.16hg.cd.trash_folder.vl.1
diff -urN mutt-1.5.24/commands.c mutt-1.5.24.new/commands.c
--- mutt-1.5.24/commands.c	2015-08-30 19:18:28.000000000 +0200
+++ mutt-1.5.24.new/commands.c	2015-12-23 22:50:08.000000000 +0100
@@ -720,6 +720,7 @@
     if (option (OPTDELETEUNTAG))
       mutt_set_flag (Context, h, M_TAG, 0);
   }
+  mutt_set_flag (Context, h, M_APPENDED, 1);
   
   return 0;
 }
diff -urN mutt-1.5.24/flags.c mutt-1.5.24.new/flags.c
--- mutt-1.5.24/flags.c	2015-08-30 19:06:38.000000000 +0200
+++ mutt-1.5.24.new/flags.c	2015-12-23 22:50:08.000000000 +0100
@@ -65,7 +65,13 @@
       {
 	h->deleted = 0;
         update = 1;
-	if (upd_ctx) ctx->deleted--;
+        if (upd_ctx)
+        {
+          ctx->deleted--;
+          if (h->appended)
+            ctx->appended--;
+        }
+        h->appended = 0; /* when undeleting, also reset the appended flag */
 #ifdef USE_IMAP
         /* see my comment above */
 	if (ctx->magic == M_IMAP) 
@@ -87,6 +93,17 @@
       }
       break;
 
+    case M_APPENDED:
+      if (bf)
+      {
+       if (!h->appended)
+       {
+         h->appended = 1;
+         if (upd_ctx) ctx->appended++;
+       }
+      }
+      break;
+
     case M_NEW:
 
       if (!mutt_bit_isset(ctx->rights,M_ACL_SEEN))
diff -urN mutt-1.5.24/globals.h mutt-1.5.24.new/globals.h
--- mutt-1.5.24/globals.h	2015-08-30 19:06:38.000000000 +0200
+++ mutt-1.5.24.new/globals.h	2015-12-23 22:50:26.000000000 +0100
@@ -141,6 +141,7 @@
 WHERE char *Status;
 WHERE char *Tempdir;
 WHERE char *Tochars;
+WHERE char *TrashPath;
 WHERE char *TSStatusFormat;
 WHERE char *TSIconFormat;
 WHERE short TSSupported;
diff -urN mutt-1.5.24/imap/message.c mutt-1.5.24.new/imap/message.c
--- mutt-1.5.24/imap/message.c	2015-08-30 19:06:38.000000000 +0200
+++ mutt-1.5.24.new/imap/message.c	2015-12-23 22:50:08.000000000 +0100
@@ -884,6 +884,7 @@
         if (ctx->hdrs[n]->tagged)
         {
           mutt_set_flag (ctx, ctx->hdrs[n], M_DELETE, 1);
+         mutt_set_flag (ctx, ctx->hdrs[n], M_APPENDED, 1);
           if (option (OPTDELETEUNTAG))
             mutt_set_flag (ctx, ctx->hdrs[n], M_TAG, 0);
         }
@@ -891,6 +892,7 @@
     else
     {
       mutt_set_flag (ctx, h, M_DELETE, 1);
+      mutt_set_flag (ctx, h, M_APPENDED, 1);
       if (option (OPTDELETEUNTAG))
         mutt_set_flag (ctx, h, M_TAG, 0);
     }
diff -urN mutt-1.5.24/init.h mutt-1.5.24.new/init.h
--- mutt-1.5.24/init.h	2015-08-30 19:06:38.000000000 +0200
+++ mutt-1.5.24.new/init.h	2015-12-23 22:50:08.000000000 +0100
@@ -3341,6 +3341,16 @@
   ** provided that ``$$ts_enabled'' has been set. This string is identical in
   ** formatting to the one used by ``$$status_format''.
   */
+  { "trash",           DT_PATH, R_NONE, UL &TrashPath, 0 },
+  /*
+  ** .pp
+  ** If set, this variable specifies the path of the trash folder where the
+  ** mails marked for deletion will be moved, instead of being irremediably
+  ** purged.
+  ** .pp
+  ** NOTE: When you delete a message in the trash folder, it is really
+  ** deleted, so that you have a way to clean the trash.
+  */
 #ifdef USE_SOCKET
   { "tunnel",            DT_STR, R_NONE, UL &Tunnel, UL 0 },
   /*
diff -urN mutt-1.5.24/mutt.h mutt-1.5.24.new/mutt.h
--- mutt-1.5.24/mutt.h	2015-08-30 19:06:38.000000000 +0200
+++ mutt-1.5.24.new/mutt.h	2015-12-23 22:50:08.000000000 +0100
@@ -185,6 +185,7 @@
   M_DELETE,
   M_UNDELETE,
   M_DELETED,
+  M_APPENDED,
   M_FLAG,
   M_TAG,
   M_UNTAG,
@@ -713,6 +714,7 @@
   unsigned int mime : 1;    		/* has a MIME-Version header? */
   unsigned int flagged : 1; 		/* marked important? */
   unsigned int tagged : 1;
+  unsigned int appended : 1; /* has been saved */
   unsigned int deleted : 1;
   unsigned int changed : 1;
   unsigned int attach_del : 1; 		/* has an attachment marked for deletion */
@@ -885,6 +887,7 @@
   int new;			/* how many new messages? */
   int unread;			/* how many unread messages? */
   int deleted;			/* how many deleted messages */
+  int appended;                 /* how many saved messages? */
   int flagged;			/* how many flagged messages */
   int msgnotreadyet;		/* which msg "new" in pager, -1 if none */
 
diff -urN mutt-1.5.24/muttlib.c mutt-1.5.24.new/muttlib.c
--- mutt-1.5.24/muttlib.c	2015-08-30 19:06:38.000000000 +0200
+++ mutt-1.5.24.new/muttlib.c	2015-12-23 22:50:08.000000000 +0100
@@ -1505,7 +1505,9 @@
 
   if (magic > 0 && !mx_access (s, W_OK))
   {
-    if (option (OPTCONFIRMAPPEND))
+    if (option (OPTCONFIRMAPPEND) &&
+       (!TrashPath || (mutt_strcmp (s, TrashPath) != 0)))
+      /* if we're appending to the trash, there's no point in asking */
     {
       snprintf (tmp, sizeof (tmp), _("Append messages to %s?"), s);
       if ((rc = mutt_yesorno (tmp, M_YES)) == M_NO)
diff -urN mutt-1.5.24/mx.c mutt-1.5.24.new/mx.c
--- mutt-1.5.24/mx.c	2015-08-30 19:06:38.000000000 +0200
+++ mutt-1.5.24.new/mx.c	2015-12-23 22:50:08.000000000 +0100
@@ -776,6 +776,53 @@
   return rc;
 }
 
+/* move deleted mails to the trash folder */
+static int trash_append (CONTEXT *ctx)
+{
+    CONTEXT *ctx_trash;
+    int i = 0;
+    struct stat st, stc;
+
+    if (!TrashPath || !ctx->deleted ||
+       (ctx->magic == M_MAILDIR && option (OPTMAILDIRTRASH)))
+      return 0;
+
+    for (;i < ctx->msgcount && (!ctx->hdrs[i]->deleted ||
+                               ctx->hdrs[i]->appended); i++);
+    if (i == ctx->msgcount)
+      return 0; /* nothing to be done */
+
+    if (mutt_save_confirm (TrashPath, &st) != 0)
+    {
+      mutt_error _("message(s) not deleted");
+      return -1;
+    }
+
+    if (lstat (ctx->path, &stc) == 0 && stc.st_ino == st.st_ino
+       && stc.st_dev == st.st_dev && stc.st_rdev == st.st_rdev)
+      return 0;  /* we are in the trash folder: simple sync */
+
+    if ((ctx_trash = mx_open_mailbox (TrashPath, M_APPEND, NULL)) != NULL)
+    {
+      for (i = 0 ; i < ctx->msgcount ; i++)
+       if (ctx->hdrs[i]->deleted && !ctx->hdrs[i]->appended
+           && mutt_append_message (ctx_trash, ctx, ctx->hdrs[i], 0, 0) == -1)
+         {
+           mx_close_mailbox (ctx_trash, NULL);
+           return -1;
+         }
+
+      mx_close_mailbox (ctx_trash, NULL);
+    }
+    else
+    {
+      mutt_error _("Can't open trash folder");
+      return -1;
+    }
+
+    return 0;
+}
+
 /* save changes and close mailbox */
 int mx_close_mailbox (CONTEXT *ctx, int *index_hint)
 {
@@ -912,6 +959,7 @@
 	  if (mutt_append_message (&f, ctx, ctx->hdrs[i], 0, CH_UPDATE_LEN) == 0)
 	  {
 	    mutt_set_flag (ctx, ctx->hdrs[i], M_DELETE, 1);
+            mutt_set_flag (ctx, ctx->hdrs[i], M_APPENDED, 1);
 	  }
 	  else
 	  {
@@ -936,6 +984,14 @@
     return 0;
   }
   
+  /* copy mails to the trash before expunging */
+  if (purge && ctx->deleted)
+    if (trash_append (ctx) != 0)
+    {
+      ctx->closing = 0;
+      return -1;
+    }
+
 #ifdef USE_IMAP
   /* allow IMAP to preserve the deleted flag across sessions */
   if (ctx->magic == M_IMAP)
@@ -1133,6 +1189,12 @@
   msgcount = ctx->msgcount;
   deleted = ctx->deleted;
 
+  if (purge && ctx->deleted)
+  {
+    if (trash_append (ctx) == -1)
+      return -1;
+  } 
+
 #ifdef USE_IMAP
   if (ctx->magic == M_IMAP)
     rc = imap_sync_mailbox (ctx, purge, index_hint);
diff -urN mutt-1.5.24/postpone.c mutt-1.5.24.new/postpone.c
--- mutt-1.5.24/postpone.c	2015-08-30 19:06:38.000000000 +0200
+++ mutt-1.5.24.new/postpone.c	2015-12-23 22:50:08.000000000 +0100
@@ -277,6 +277,9 @@
   /* finished with this message, so delete it. */
   mutt_set_flag (PostContext, h, M_DELETE, 1);
 
+  /* and consider it saved, so that it won't be moved to the trash folder */
+  mutt_set_flag (PostContext, h, M_APPENDED, 1);
+
   /* update the count for the status display */
   PostCount = PostContext->msgcount - PostContext->deleted;