If you only know a member's email address and need to look up their User, use the Find a Member feature. This feature is useful if you receive emails from members who haven't specified their User ID and you cannot locate their listing.

For privacy reasons eBay limits the use of this feature to those members who have completed a previous transaction with the member whose User ID is being requested.

If you have not completed a transaction with the member eBay will provide only limited information about the member to ensure privacy. If eBay cannot determine a transactional relationship you should request the member to send you their User ID via email.