Our University recently had a case where some notorious fellows used a fake emailing service to send an email to all students on behalf of the administration. Although most good email services (like Gmail?) can warn us that the mail is likely a phishing attempt, many users not educated in security may fall in this trap.
My understanding of emails (I am no pro, so pardon me if there are flaws) was that if I need to use something like Telnet to send fake emails with a local email service (on LAN), it would be anyways possible, but I would need to enabling some kind of 'relay' to be able to do so for services like Gmail.
My question here: how is this fake emailer (or any other) doing this? I am not looking for theory on email. Maybe some security guys could have a look at the page's source and give clearer details.