Why can't personal certificates do this? (Score 4, Informative)

Can I ask what happened to using Personal certificates?? Why, when we use SSL certificates to verify that a website we are visting is actually the true company, can't we use personal certificates to verify that the email we are reciving is actually from the company?? Surely they could configure their mail servers to filter out email on this basis without requiring a 3rd part solution that makes you pay for it. Hate to state the obvious but this is just the big companies way to getting their hands in on a great free thing that the internet provides