Gmail does not specifically frown on Gmail extensions that reveal email open rates. You must, however, be cautious about privacy concerns. Gmail prioritizes user experience and privacy. Some email tracking extensions may violate Gmail's privacy policies. You need to ensure the extension you use complies with these policies. Your emails must not compromise user privacy. You should also avoid using tracking methods that could be considered invasive. Gmail may limit or block email accounts using questionable tracking techniques. You must focus on ethical email marketing practices. Respecting user privacy helps maintain a good relationship with Gmail and your audience.