[ci skip] Fix #4613
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;
 	}