The magic tool is Whois.com.
this list the owner of an particular domain name.
It also lists the registered address and the country where it is registered.
One of the down sides of the web is that some one in Upper Nowhereasstan can buy domains in any country in the world.
thus the scammers can end up with ligitermate looking address ,e.g;- .com.au or .biz.uk etc etc etc.
I have broadband ( well pretend broadband here in OZ ) and the beauty of this is you get almost unlimited email addresses so I use about 15 or so.
I keep a dummy address that I never check as the contact email for all lists & forums ( like this one ) thus the web bots can only get an email address that I actually do not use.
There is a different one that only ever gets used for Paypal so any message from any one else other than Paypal in this mail box is a scam and obversely any paypal email in any other one is also a scam.
I use a different one exclusively for evilbay, note not the same one as paypal.
There is another for BSA related stuff
One excluseivly for internet banking for my business account ( I do not do electronic banking but do get electronic statements and occasionally check balances ).
Another for my private banking
Another for the credit union.
Another for Rollers & the old wedding car business
Another for the mower repair business.
Another for family contacts
Another from a previous courier contract ( 4 of these )
The beauty of this is most scams are broadcast so when something from the bank I do business with appears, addressed to me personally, in the wrong email in box, it is a scam.
It is amazing how good some of the fake sites are.
If it is an email, try printing it, Some where in the options will be "detailed headder" or something similar. This will add the entire routing as a headder to the email and you then check it out using the "preview" option.
If you see it originated in one country then seems to have bounced around the globe 20 times, it is fake as a real deal will have a single origin and if it is from your bank it will be @barclays.co.uk .
I once had one from @anzhomeloans.com.au which looked light but the check on these is to try
www.anzhomeloans.com.au,
if there is no web page attached to the URL it is a fake.