We at a company would like to publish a whitepaper to be included in the proceedings of an academic conference. The specified format requires us to list all authors together with their e-mail addresses.
One author (who did about 5% of the work) had parted ways with the company about half a year ago and had no connection with the ongoing research (or members of the research group) at all since. Thus he doesn't possess a company e-mail address any more either.
How should such a person listed among the authors? He contributed to the research, so naturally should be listed but I'd prefer to do it in a way that communicates "I have no connection with the group any more, I don't know about recent developments and if you contact me most possibly I won't be able to tell you too much useful information". Also, is it suitable to include his personal e-mail address?