Our Purchase Orders suddenly are being automatically sent out via email. I don't know of any changes made to the system - the Setup/Company/Email Preference is not selected, neither is it selected on the vendor record. Any ideas?

Have you checked any workflows running on your purchase orders? Go to Customization > Scripting > Scripted Records > Purchase Order.

I'm the only one who knows how to create workflows. 😞

Could that be coming from a saved search that is email enabled?

That's a thought...