diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index ed6f737..cdfb43b 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -2153,6 +2153,11 @@
 			return FALSE;
 		}
 
+		if ($this->smtp_keepalive)
+		{
+			$this->_smtp_auth = FALSE;
+		}
+
 		return TRUE;
 	}
 
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index d50c0a0..567eb10 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -27,6 +27,7 @@
 -  Fixed a bug (#4562) - :doc:`Cache Library <libraries/caching>` didn't check if ``Memcached::quit()`` is available before calling it.
 -  Fixed a bug (#4563) - :doc:`Input Library <libraries/input>` method ``request_headers()`` ignores ``$xss_clean`` parameter value after first call.
 -  Fixed a bug (#4605) - :doc:`Config Library <libraries/config>` method ``site_url()`` stripped trailing slashes from relative URIs passed to it.
+-  Fixed a bug (#4613) - :doc:`Email Library <libraries/config>` failed to send multiple emails via SMTP due to "already authenticated" errors when keep-alive is enabled.
 
 Version 3.0.6
 =============