diff -r a8003c55a83e mbyte.c
--- a/mbyte.c	Wed Mar  1 11:02:27 2006
+++ b/mbyte.c	Sat Mar  4 23:44:29 2006
@@ -469,3 +469,36 @@
 {
   return Charset_is_utf8 ? 0xfffd : '?';
 }
+
+int mutt_filter_unprintable (char **s)
+{
+  BUFFER *b = NULL;
+  wchar_t wc;
+  size_t k, k2;
+  char scratch[MB_LEN_MAX + 1];
+  char *p = *s;
+  mbstate_t mbstate1, mbstate2;
+
+  if (!(b = mutt_buffer_init (b)))
+    return -1;
+  memset (&mbstate1, 0, sizeof (mbstate1));
+  memset (&mbstate2, 0, sizeof (mbstate2));
+  for (; (k = mbrtowc (&wc, p, MB_LEN_MAX, &mbstate1)); p += k)
+  {
+    if (k == (size_t)(-1) || k == (size_t)(-2))
+    {
+      k = 1;
+      wc = replacement_char();
+    }
+    if (!IsWPrint (wc))
+      wc = '?';
+    k2 = wcrtomb (scratch, wc, &mbstate2);
+    scratch[k2] = '\0';
+    mutt_buffer_addstr (b, scratch);
+  }
+  FREE (s);
+  *s = b->data;
+  FREE (&b);
+  return 0;
+}
+
diff -r a8003c55a83e protos.h
--- a/protos.h	Wed Mar  1 11:02:27 2006
+++ b/protos.h	Sat Mar  4 23:44:29 2006
@@ -181,6 +181,7 @@
 void mutt_edit_content_type (HEADER *, BODY *, FILE *);
 void mutt_edit_file (const char *, const char *);
 void mutt_edit_headers (const char *, const char *, HEADER *, char *, size_t);
+int mutt_filter_unprintable (char **);
 void mutt_curses_error (const char *, ...);
 void mutt_curses_message (const char *, ...);
 void mutt_enter_command (void);
diff -r a8003c55a83e rfc2047.c
--- a/rfc2047.c	Wed Mar  1 11:02:27 2006
+++ b/rfc2047.c	Sat Mar  4 23:44:29 2006
@@ -705,6 +705,7 @@
   
   if (charset)
     mutt_convert_string (&d0, charset, Charset, M_ICONV_HOOK_FROM);
+  mutt_filter_unprintable (&d0);
   strfcpy (d, d0, len);
   FREE (&charset);
   FREE (&d0);
diff -r a8003c55a83e rfc2231.c
--- a/rfc2231.c	Wed Mar  1 11:02:27 2006
+++ b/rfc2231.c	Sat Mar  4 23:44:29 2006
@@ -131,6 +131,7 @@
       s = rfc2231_get_charset (p->value, charset, sizeof (charset));
       rfc2231_decode_one (p->value, s);
       mutt_convert_string (&p->value, charset, Charset, M_ICONV_HOOK_FROM);
+      mutt_filter_unprintable (&p->value);
 
       *last = p;
       last = &p->next;