FYI, unless the (alleged) sender's domain has got SPF records and your mail server implements it, anyone can just change his 'From:' address to whatever he wants just by going to 'Settings...' in the mail client.

Actually bitcointalk.org *does* have an SPF record protecting it with a strict (-all) policy: according to standards, the phishing message should have been rejected, but your mail server probably doesn't enforce the requested policy. Funny thing is that a domain such as 'whitehouse.gov' uses a relaxed policy (~all), so phishing e-mails from 'whitehouse.gov' would en up in your spam folder at best