Retrieve user ids (or even emails) of people who installed my plugin?

If you want to have your plugin listed in the WP repository, any sort of communication scheme between the site owner and yourself must be on an opt in basis. If you don’t care about that kind of promotion, there’s all sorts of information available that your plugin could send to you, starting with the admin email, and much more. A lot of users would take offense of plugins that ‘phone home’ without their approval. I urge you to not consider such a scheme except as an opt in feature.

Thanks for your answer, no my goal was not to steal anything, rather to send an information email thru www.remarpro.com platform, just as if my plugin users were subscribed to an info feed about it.
But ok i understand it’s actually up to me to redirect them (or offer them subscription in the WP back office) to my site and freely make them opt-in.
Cheers