The user agent I saw looks like a normal client that a person might use: 74.51.221.37 - - [19/Aug/2021:22:05:16 +0000] "GET /validate/email/1d00a5c2648c211befd

The user agent I saw looks like a normal client that a person might use: 74.51.221.37 - - [19/Aug/2021:22:05:16 +0000] "GET /validate/email/1d00a5c2648c211befd33f5a8a7cbfab HTTP/1.1" 404 0 "" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.107 Safari/537.36" I suppose you could somehow block cache.google.com but I suspect Microsoft and others do similar things.