And your sales people will call this a misconfiguration serious enough to fire the sysadmin who did this. The problem is that, typically, nobody trains or supervises the filter applied to the outgoing mail, and nobody is warned that it did, in fact, reject an email, and there is no manual override if the filter is, in fact, wrong. And spammers (from the viewpoint of a particular organization) don't exist and can't exist inside the organization, so any rejected outgoing email is, by definition, a false positive.
Well, viruses are the exception.