stewartcs is correct, if the information is going to be anywhere it's going to be in the message headers. But don't depend on this, it's easily spoofed or faked. If an SMTP server accepts an attacker's relay he can tell it the message came from wherever he wants to and there's no way to verify it. (Well, there's something called an SPF DNS entry which is an anti-spam precaution, but it's optional and anyways you'd need access to the records of every mail server in the delivery chain to confirm it 100%.)
If you're using webmail, then the answer to your questions depends on what webmail service you're using. Look through the help for whatever service you have, or look for buttons that say things like "Show Details" or "Show Headers" or "Show Original."