I'm a home user that is a tad ignorant on digital signature troubleshooting. I received two e-mails that contained "invalid Digital Signature" in the preview pane, and said for details to open the mail. This is the first time I have ever received e-mail like this and these were from a friend who normally sends several e-mails a day. Suspicious as I am, I deleted them instead of opening them, particularly since I have never seen this type of message (?) error (?) before. I have searched all the security sites I can find, and they all tell you how to do digital signatures, but nothing tells what to do when one is received. I think whatever it may be, that I am safe: my MS patches are all up to date( I keep them that way) and I have active virus protection via Norton, email scans in/out, auto liveupdate, etc. I have detected virus's from others when e-mail comes in and I have been able to trace them back to get the victim to get rid of the virus and get them on virus protection, but I'm not sure what to do about this. Is it "safe" to open when it has this message and what could be the possible culprit? - yes, it means it's not valid, but is there a known virus, worm or something out there causing this type of effect? Thanks in advance for your replies.