diff --git a/src/LaunchDarkly/GuzzleEventPublisher.php b/src/LaunchDarkly/GuzzleEventPublisher.php
index ce18f0f14..7dc458950 100644
--- a/src/LaunchDarkly/GuzzleEventPublisher.php
+++ b/src/LaunchDarkly/GuzzleEventPublisher.php
@@ -60,9 +60,13 @@ public function publish($payload)
             $this->_logger->warning("GuzzleEventPublisher::publish caught $e");
             return false;
         }
-        if ($response && ($response->getStatusCode() == 401)) {
-            throw new InvalidSDKKeyException();
+        if ($response && ($response->getStatusCode() >= 300)) {
+            $this->_logger->error(Util::httpErrorMessage($response->getStatusCode(), 'event posting', 'some events were dropped'));
+            if (!Util::isHttpErrorRecoverable($response->getStatusCode())) {
+                throw new UnrecoverableHTTPStatusException($response->getStatusCode());
+            }
+            return false;
         }
-        return $response && ($response->getStatusCode() < 300);
+        return $response != null;
     }
 }
diff --git a/src/LaunchDarkly/GuzzleFeatureRequester.php b/src/LaunchDarkly/GuzzleFeatureRequester.php
index 65f446d8d..efd40c59c 100644
--- a/src/LaunchDarkly/GuzzleFeatureRequester.php
+++ b/src/LaunchDarkly/GuzzleFeatureRequester.php
@@ -115,9 +115,9 @@ public function getAllFeatures()
 
     private function handleUnexpectedStatus($code, $method)
     {
-        $this->_logger->error("$method received an unexpected HTTP status code $code");
-        if ($code == 401) {
-            throw new InvalidSDKKeyException();
+        $this->_logger->error(Util::httpErrorMessage($code, $method, 'default value was returned'));
+        if (!Util::isHttpErrorRecoverable($code)) {
+            throw new UnrecoverableHTTPStatusException($code);
         }
     }
 }
diff --git a/src/LaunchDarkly/InvalidSDKKeyException.php b/src/LaunchDarkly/InvalidSDKKeyException.php
deleted file mode 100644
index 7eb7795bb..000000000
--- a/src/LaunchDarkly/InvalidSDKKeyException.php
+++ /dev/null
@@ -1,9 +0,0 @@
-<?php
-namespace LaunchDarkly;
-
-/**
- * Used internally.
- */
-class InvalidSDKKeyException extends \Exception
-{
-}
diff --git a/src/LaunchDarkly/LDClient.php b/src/LaunchDarkly/LDClient.php
index 5f0ae10b8..4d2ac10b1 100644
--- a/src/LaunchDarkly/LDClient.php
+++ b/src/LaunchDarkly/LDClient.php
@@ -146,8 +146,8 @@ public function variation($key, $user, $default = false)
             }
             try {
                 $flag = $this->_featureRequester->getFeature($key);
-            } catch (InvalidSDKKeyException $e) {
-                $this->handleInvalidSDKKey();
+            } catch (UnrecoverableHTTPStatusException $e) {
+                $this->handleUnrecoverableError();
                 return $default;
             }
 
@@ -275,8 +275,8 @@ public function allFlags($user)
         }
         try {
             $flags = $this->_featureRequester->getAllFeatures();
-        } catch (InvalidSDKKeyException $e) {
-            $this->handleInvalidSDKKey();
+        } catch (UnrecoverableHTTPStatusException $e) {
+            $this->handleUnrecoverableError();
             return null;
         }
         if ($flags === null) {
@@ -314,8 +314,8 @@ public function flush()
     {
         try {
             return $this->_eventProcessor->flush();
-        } catch (InvalidSDKKeyException $e) {
-            $this->handleInvalidSDKKey();
+        } catch (UnrecoverableHTTPStatusException $e) {
+            $this->handleUnrecoverableError();
         }
     }
 
@@ -345,9 +345,9 @@ protected function _get_default($key, $default)
         }
     }
 
-    protected function handleInvalidSDKKey()
+    protected function handleUnrecoverableError()
     {
-        $this->_logger->error("Received 401 error, no further HTTP requests will be made during lifetime of LDClient since SDK key is invalid");
+        $this->_logger->error("Due to an unrecoverable HTTP error, no further HTTP requests will be made during lifetime of LDClient");
         $this->_offline = true;
     }
 }
diff --git a/src/LaunchDarkly/UnrecoverableHTTPStatusException.php b/src/LaunchDarkly/UnrecoverableHTTPStatusException.php
new file mode 100644
index 000000000..4e1b5ad44
--- /dev/null
+++ b/src/LaunchDarkly/UnrecoverableHTTPStatusException.php
@@ -0,0 +1,15 @@
+<?php
+namespace LaunchDarkly;
+
+/**
+ * Used internally.
+ */
+class UnrecoverableHTTPStatusException extends \Exception
+{
+    public $status;
+
+    public function __construct($status)
+    {
+        $this->status = $status;
+    }
+}
diff --git a/src/LaunchDarkly/Util.php b/src/LaunchDarkly/Util.php
index f25f241e0..1fbf79010 100644
--- a/src/LaunchDarkly/Util.php
+++ b/src/LaunchDarkly/Util.php
@@ -51,4 +51,30 @@ public static function newFeatureRequestEvent($key, $user, $variation, $value, $
         $event['prereqOf'] = $prereqOf;
         return $event;
     }
+
+    /**
+     * @param $status int
+     * @return boolean
+     */
+    public static function isHttpErrorRecoverable($status)
+    {
+        if ($status >= 400 && $status < 500) {
+            return ($status == 400) || ($status == 408) || ($status == 429);
+        }
+        return true;
+    }
+
+    /**
+     * @param $status int
+     * @param $context string
+     * @param $retryMessage string
+     * @return string
+     */
+    public static function httpErrorMessage($status, $context, $retryMessage)
+    {
+        return 'Received error ' . $status
+            . (($status == 401) ? ' (invalid SDK key)' : '')
+            . ' for ' . $context . ' - '
+            . (Util::isHttpErrorRecoverable($status) ? $retryMessage : 'giving up permanently');
+    }
 }