/errors/authentication_error.proto 

--- v22/errors/authentication_error.proto   2026-01-23 15:36:22.000000000 +0000
+++ v23/errors/authentication_error.proto   2026-01-23 15:36:26.000000000 +0000
@@ -85,6 +85,9 @@
     // Login cookie is not valid.
     LOGIN_COOKIE_INVALID = 20;

+    // The email address provided is invalid or does not exist.
+    INVALID_EMAIL_ADDRESS = 21;
+
     // User ID in the header is not a valid ID.
     USER_ID_INVALID = 22;