Hey there!
We are in need of a survey that is open for people I contact via a newsletter. We are evaluating these people's opinion on a given topic and need a certain level of anonymity in order to make them submit honest results. However, we also want to contact participants with a vide variety of opinions afterwards, so it must be possible to contact the person who submitted a specific dataset. What I might imagine is a list/database linking the datasets' ids to email-adresses submitted in the survey, so that we could re-establish the identity of some people without immediately seeing who gave which answers.
woah, I hope I could somhow make clear what we need..
Thanks a lot!

This would rather defeat the point of anonimity, personally I'ld be surprised (not to mention annoyed) if I got a tailored follow-up survey to a supposedly anonymous survey.

Why not just be honest and say responses will be handled confidentially (or possibly even anonimized), but we might use your e-mail address to ask follow-up questions? You could put extra emphasis on not using individual results if that is indeed the case.

My point is, what you're suggesting is at best shady from an ethical perspective, and will probably alienate respondents more than being clear up front.

I agree with Karel. You can't have anonymity AND be able to recontact people based on certain answers. This is totally contrary the idea of anonymity in the first place.

Be open about things.