I received an email as well and was likewise, dubious. But if it was a phishing attempt they went to alot of trouble, as they knew my "handle" and the 25 caches they want me to check are all legit and geolocated close to my home. Unfortunately, many of them were rough to find and I'm not sure I have those bushwhacks in me again. To get better participation, they need to do a little better job identifying themselves in this process, as it comes across as "phishy". The word "Groundspeak" appears nowhere so I also was wary.