Sort of a CRM, but not quite

Hi,

I run a small nonprofit, and am desperately in need of something like a CRM, but maybe not quite. We work with volunteers who in turn work at large organizations, usually businesses, and partly involve their employers in their work with us. We also run a lot of events for which people sign up, creating problems of duplicates. To make a long story short, neither business nor personal emails are ideal as unique IDs, because people stay with us after job changes, but we usually start with their business emails. I would like to use LinkedIn address as the ID. Every CRM I've looked at uses a single email field as the Unique ID. Do you know of any that will let me set the ID field to LinkedIn for things like uploads or signup forms? Thanks!