Elparts saves IP addresses of logged-in users to determine their country and for security/logging and statistics.
E-mail addresses of registered users are saved in a database and never shared with any third party. They are used solely as user identification for login, and as recovery means in case of forgotten password. E-mail address is also displayed on click on a user name (in a hardened form against bots) if a user has some parts in their inventory - to allow for contact from an eventual buyer of the parts. No spam is ever sent to these e-mail addresses - I don't like spam either.
For EU users - the DPO is the author of Elparts. Any questions? Write me an e-mail.