How does CacheCam know my User ID if I don include it in the request?
When you send a grab request to CacheCam, and don’t include your User ID, the system tries to figure out who you are by checking the sender’s address in the email that it receives. If it can match that address against a Reply-to or Alert-to email address in a registered user’s profile, then it assumes that you are that user. From there it can use the User ID it finds to check waypoint presets and the other grab defaults. This is especially useful if you tend to use your phone a lot for webcam geocaching. By including your phone’s email address in the Alert-to (or the Reply-to) default setting, whenever you send a grab request to CacheCam from your phone it will automatically identify you as the requester and use your waypoints and grab defaults, as if you had included them (or your user ID) in the actual request. In this way, you can do a phone grab request by typing only a few characters, that is, simply the waypoint name.
