You would think so.. but its remarkable how easy it still is to forge email.
My mum was recently the target of such a campaign. She's in the executive team at an international NGO. An attacker found her email address and a bunch of her contacts via the NGO's webpage. Then they forged emails from her email address, with a gmail address set up in the reply-to field. The emails all said it was an emergency, and asked for her colleages to transfer money.
As far as we can tell, most of the emails were delivered and lots of people were fooled - at least for awhile.
Her email address has DKIM and SPF set up, but (like most email providers) it has a lax DMARC policy. It turns out thats all it takes to be vulnerable to this sort of attack.
