I know almost nothing about security. So, please bear with me if the questions sound silly.
Is it possible for a malicious person to make an e-mail appear as if it came from a big company like Google, Apple, Cisco etc ? If yes, what kind of techniques do they use and how to detect these fake e-mails ?
Another thing - I guess that big companies like these must be having different servers to send out official e-mails. Is it possible for someone to create a fake server or add their own server to the company server list and then send malicious e-mails from it ?
Also, could someone silently hijack a company's mail server, send malicious e-mails to a few targets only to avoid detection ?