Rated 5 out of 5 stars
This is an excellent extension but as mentioned in other reviews, the DomainKeys verification is currently broken. I got the working code for SenderVerification.pm and query.cgi from archive.org, and set up my own verification server. In the extension settings, set your DK Verification Server to:
You can also view SenderVerification.pm.txt and query.cgi.txt in that same location to get the source and set up your own server.