Why Does Have I Been Pwned Contain "Fake" Email Addresses? (www.troyhunt.com)

Have I Been Pwned (HIBP) addresses misunderstandings regarding the presence of "fake" email addresses in its database, sparked by a critical Trustpilot review. The founder clarifies that HIBP processes breach data by extracting valid email addresses based on simple structural criteria, such as the presence of an "@" symbol and a valid domain. However, this does not guarantee that the email has an existing mailbox, as verifying each would be impractical given HIBP's vast dataset of 7 billion unique addresses. Consequently, even placeholders like "foo@bar.com" can end up in the database if they meet the structural requirements. This explanation highlights an important aspect of data integrity and understanding in the AI/ML community, especially for those relying on data quality from external sources. It reveals a gap in how organizations like Adobe handle user sign-ups—often failing to verify email addresses effectively. As a result, valid but non-existent addresses may proliferate in breached datasets, reinforcing the need for more rigorous validation processes to enhance data accuracy. HIBP's transparency in its operating procedures serves as a reminder of the complexities of data ingestion and the importance of critical evaluation of data sources.