We use in-house Exchange 2010.
We recently have received some impersonating emails pretending our CEO as the sender. The emails were sent to our Accounting Account Payable, Controller, etc asking to send money to some address or bank account. The emails are just with a perfect format including signature, name, greeting, receiving addresses, etc., which make them nearly authenticate to the recipients. Our CEO has a great concern that they many contact someone at the office and get valuable information or cash without them knowing it is from an impersonator. Can you tell me how to stop them?
From the header, we can see the real sender's email address, etc. What can we do to stop them?