Stopping Phishers via SPF

There are a number of technologies currently being developed to help combat spam, phishing fraud and other email related abuse.
One which has received a considerable amount of attention in recent months is SPF. Another, which may not have attracted quite as much attention, is Yahoo’s domain keys.
In both instances the technology is designed to help verify who is authorised to send mail from a particular server, hostname or IP address.
The problem, if you aren’t a diehard geek, is actually identifying potential fraud in your email client.
Server-side (at the MTA level) implementation comes in a number of forms, but at the client level (desktop) the number of email clients that actually check for valid SPF records (or domain keys) is thin on the ground.
For Thunderbird you can install Joshua Tauberer’s handy little extension which checks both SPF and Yahoo Domain Keys
I’d love to hear of other email clients that support these kind of checks.