The problem isn't the failure messages per se, it's the failure messages regarding user error. If the user has made a mistake somewhere, the client should try

The problem isn't the failure messages per se, it's the failure messages regarding user error. If the user has made a mistake somewhere, the client should try to understand the error message and, if it's user error (email address doesn't exist, attachment too big), it should suggest solutions to the problem in a language the user can understand. If the system itself has an issue, the client should provide enough information to tell the user either: a) How they can resolve it b) How they can contact whoever needs to resolve it