PayPal aggressively rate-limits its public endpoints. After just 5-10 requests from the same IP, you’ll hit a CAPTCHA. After 20, your IP is temporarily blocked. After 50, your PayPal account (if used in the checker) is flagged for review.
PayPal employs sophisticated bot-detection mechanisms (such as CAPTCHAs, rate limiting, and IP blocking) to prevent automated scripts from checking millions of emails. They also obscure user details; for example, when sending money, the platform may not display the recipient's full name until the transaction is further along the pipeline, specifically to prevent "harvesting" of user data. paypal valid email checker
High bounce rates (over 2%) can cause providers like Gmail or Outlook to flag your domain as spam. PayPal aggressively rate-limits its public endpoints