Sounds to me like it's a 'problem' with one of the email addresses you are sending to--that particular email server has some kind of filter on it. The error message might also indicated which email address was directed. The error message you posted said 'one' of the receipients was rejected. E-smith has no such limit. We send out hundreds at a time without fail. If you can't get it figured out, post the whole error message and the messages source.