Index: privatemsg.api.php
===================================================================
RCS file: /cvs/drupal/contributions/modules/privatemsg/privatemsg.api.php,v
retrieving revision 1.3
diff -u -p -r1.3 privatemsg.api.php
--- privatemsg.api.php	6 Jul 2010 18:03:07 -0000	1.3
+++ privatemsg.api.php	15 Aug 2010 13:04:23 -0000
@@ -403,13 +403,16 @@ function hook_privatemsg_message_recipie
  *
  * @param $author
  *   Author of the message to be sent
- * @param $recipient
+ * @param $recipients
  *   Recipient of the message
+ * @param $context
+ *   Additional information. Can contain the thread_id to indicate that this is
+ *   a reply on an existing thread.
  * @return
  *   An indexed array of arrays with the keys recipient ({type}_{key}) and
  *   message (The reason why the recipient has been blocked).
  */
-function hook_privatemsg_block_message($author, $recipients) {
+function hook_privatemsg_block_message($author, $recipients, $context = array()) {
   $blocked = array();
   foreach($recipients as $recipient_id => $recipient) {
     // Deny/block if the recipient type is role and the account does not have
Index: privatemsg.module
===================================================================
RCS file: /cvs/drupal/contributions/modules/privatemsg/privatemsg.module,v
retrieving revision 1.144
diff -u -p -r1.144 privatemsg.module
--- privatemsg.module	5 Aug 2010 09:17:54 -0000	1.144
+++ privatemsg.module	15 Aug 2010 13:04:25 -0000
@@ -1504,7 +1504,7 @@ function _privatemsg_validate_message(&$
   }
 
   if (!empty($message['recipients']) && is_array($message['recipients'])) {
-    foreach (module_invoke_all('privatemsg_block_message', $message['author'], $message['recipients']) as $blocked) {
+    foreach (module_invoke_all('privatemsg_block_message', $message['author'], $message['recipients'], $message) as $blocked) {
       unset($message['recipients'][$blocked['recipient']]);
       if ($form) {
         // Don't display information about blocked users when replying.
@@ -1992,7 +1992,7 @@ function privatemsg_thread_change_delete
 /**
  * Implements hook_privatemsg_block_message().
  */
-function privatemsg_privatemsg_block_message($author, $recipients) {
+function privatemsg_privatemsg_block_message($author, $recipients, $context = array()) {
   $blocked = array();
   if (privatemsg_is_disabled($author)) {
     $blocked[] = array(
Index: privatemsg.pages.inc
===================================================================
RCS file: /cvs/drupal/contributions/modules/privatemsg/privatemsg.pages.inc,v
retrieving revision 1.13
diff -u -p -r1.13 privatemsg.pages.inc
--- privatemsg.pages.inc	12 Aug 2010 08:07:25 -0000	1.13
+++ privatemsg.pages.inc	15 Aug 2010 13:04:25 -0000
@@ -212,7 +212,7 @@ function privatemsg_new(&$form_state, $r
     }
 
     // Check if another module is blocking the sending of messages to the recipient by current user.
-    $user_blocked = module_invoke_all('privatemsg_block_message', $user, array(privatemsg_recipient_key($recipient) => $recipient));
+    $user_blocked = module_invoke_all('privatemsg_block_message', $user, array(privatemsg_recipient_key($recipient) => $recipient), array('thread_id' => $thread_id));
     if (!count($user_blocked) <> 0 && $recipient->recipient) {
       if ($recipient->type == 'user' && $recipient->recipient == $user->uid) {
         $usercount++;
Index: pm_block_user/pm_block_user.module
===================================================================
RCS file: /cvs/drupal/contributions/modules/privatemsg/pm_block_user/pm_block_user.module,v
retrieving revision 1.9
diff -u -p -r1.9 pm_block_user.module
--- pm_block_user/pm_block_user.module	9 Aug 2010 14:00:19 -0000	1.9
+++ pm_block_user/pm_block_user.module	15 Aug 2010 13:04:26 -0000
@@ -173,7 +173,7 @@ function _pm_block_user_rule_exists($aut
 /**
  * Implements hook_privatemsg_block_message().
  */
-function pm_block_user_privatemsg_block_message($author, $recipients) {
+function pm_block_user_privatemsg_block_message($author, $recipients, $context = array()) {
   $blocked = array();
   // Loop through each recipient and ensure there is no rule blocking this
   // author from sending them private messages. Use a reference, so when