MUAs checking SPF

Just seen in freshmeat, "Thunderbird Extension for Sender Policy
Framework".  At first blush, this appears to be more along the lines of
PRA, not SPF, checking.  The rush to implement these kinds of things FOR
USERS could be (or has been, take your pick) problematic for SPF.


Thunderbird Extension for Sender Policy Framework

http://taubz.for.net/code/spf/

        The extension looks for the email address of the sender in the
        From: header (ex. sender(_at_)aol(_dot_)com), and it looks for the IP
        address of the server that sent the email from the first
        Received: header (ex. 124.125.100.50). It then contacts a query
        server, sending it the email address and IP address, which
        responds with whether that server is permitted to send email for
        the domain name of the email address (ex. aol.com).