env->to->mailbox = safe_strdup ("undisclosed-recipients:;");
void mutt_prepare_envelope (ENVELOPE *env){  char buffer[LONG_STRING];  if (env->bcc && !(env->to || env->cc))  {    /* some MTA's will put an Apparently-To: header field showing the Bcc:     * recipients if there is no To: or Cc: field, so attempt to suppress     * it by using an empty To: field.     */    env->to = rfc822_new_address ();    env->to->mailbox = safe_strdup ("undisclosed-recipients:;");    env->to->group = 1;    env->to->next = rfc822_new_address ();     buffer[0] = 0;    rfc822_cat (buffer, sizeof (buffer), env->to->mailbox, RFC822Specials);    env->to->mailbox = safe_strdup (buffer);  }  mutt_set_followup_to (env);  /* Take care of 8-bit => 7-bit conversion. */  rfc2047_encode_adrlist (env->to);  rfc2047_encode_adrlist (env->cc);  rfc2047_encode_adrlist (env->from);  rfc2047_encode_adrlist (env->mail_followup_to);  if (env->subject)  {    rfc2047_encode_string (buffer, sizeof (buffer) - 1,			   (unsigned char *) env->subject);    safe_free ((void **) &env->subject);    env->subject = safe_strdup (buffer);  }  encode_headers (env->userhdrs);  if (!env->message_id)    env->message_id = mutt_gen_msgid ();}