+ * @new_folder: the new instance of the #TnyFolder that has been transferred
+ * @user_data: generic data passed to user defined function.
+ *
+ * This function will be called after transfer_msgs_cb private function, which is
+ * used as tinymail operation callback. The private function fills private
+ * fields of mail operation and calls user defined callback if it exists.
+ */
+typedef void (*XferMsgsAsyncUserCallback) (ModestMailOperation *mail_op,
+ gpointer user_data);
+
+
+/**
+ * XferFolderAsyncUserCallback:
+ *
+ * @obj: a #GObject generic object which has created current mail operation.
+ * @new_folder: the new instance of the #TnyFolder that has been transferred
+ * @user_data: generic data passed to user defined function.
+ *
+ * This function will be called after transfer_msgs_cb private function, which is
+ * used as tinymail operation callback. The private function fills private
+ * fields of mail operation and calls user defined callback if it exists.
+ */
+typedef void (*XferFolderAsyncUserCallback) (ModestMailOperation *mail_op,
+ TnyFolder *new_folder,
+ gpointer user_data);
+
+
+/**
+ * RefreshAsyncUserCallback:
+ *
+ * @mail_op: the current #ModestMailOperation.
+ * @folder: a #TnyFolder which has been refreshed .
+ * @user_data: generic data passed to user defined function.
+ *
+ * This function will be called after refresh_folder_async_cb private function, which is
+ * used as tinymail operation callback. The private function fills private
+ * fields of mail operation and calls user defined callback if it exists.
+ */
+typedef void (*RefreshAsyncUserCallback) (ModestMailOperation *mail_op,
+ TnyFolder *folder,
+ gpointer user_data);
+
+/**
+ * UpdateAccountCallback:
+ *
+ * @self: a #ModestMailOperation
+ * @new_headers: the list of new headers received
+ * @user_data: generic data passed to user defined function.
+ *
+ * This is the callback of the update_account operation. It informs
+ * the caller about the amount of new messages that have been
+ * downloaded
+ */
+typedef void (*UpdateAccountCallback) (ModestMailOperation *self,
+ TnyList *new_headers,
+ gpointer user_data);
+
+/**
+ * SaveToDraftsCallback:
+ *
+ * @self: a #ModestMailOperation
+ * @saved_draft: the new draft message that has been saved
+ * @user_data: generic data passed to user defined function.
+ *
+ * This is the callback of the save_to_drafts operation. It returns
+ * the newly created msg stored in the Drafts folder
+ */
+typedef void (*SaveToDraftstCallback) (ModestMailOperation *self,
+ TnyMsg *saved_draft,
+ gpointer user_data);
+
+
+typedef gboolean (*RetrieveAllCallback) (GObject *source,
+ guint num_msgs,
+ guint limit);
+
+/**
+ * CreateFolderUserCallback:
+ *
+ * @mail_op: the current #ModestMailOperation.
+ * @folder: a #TnyFolder summary item.