diff --git a/src/Mailgun/Constants/Api.php b/src/Mailgun/Constants/Api.php
index 9ca998b..16eadd8 100644
--- a/src/Mailgun/Constants/Api.php
+++ b/src/Mailgun/Constants/Api.php
@@ -9,6 +9,9 @@
 
 namespace Mailgun\Constants;
 
+/**
+ * @deprecated Will be removed in 3.0
+ */
 class Api
 {
     const API_USER = 'api';
diff --git a/src/Mailgun/Constants/ExceptionMessages.php b/src/Mailgun/Constants/ExceptionMessages.php
index bd5ce2c..ab370aa 100644
--- a/src/Mailgun/Constants/ExceptionMessages.php
+++ b/src/Mailgun/Constants/ExceptionMessages.php
@@ -9,6 +9,9 @@
 
 namespace Mailgun\Constants;
 
+/**
+ * @deprecated Will be removed in 3.0
+ */
 class ExceptionMessages
 {
     const EXCEPTION_INVALID_CREDENTIALS = 'Your credentials are incorrect.';