Email credential problem

We're trying to implement the SendCredentials emails and have added the CRED_EMAIL settings in T_Defaults, including the CRED_EMAIL_FROM

However, when we try and execute it we get the error that the "From" is empty:

Soap Error System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.ArgumentException: The parameter 'from' cannot be an empty string.
Parameter name: from

Has anyone experienced this, and know the answer?

Thanks