Rocket Chat's password reset feature fails if the user has uppercase characters in their email address, e.g. John.Doe@example.com. An issue has been raised. Until it is resolved, a possible workaround is to convert all your users' email addresses to lowercase.
This solution converts all upper case email addresses to lower case. It assumes that Rocket Chat is run through docker compose, but can easily be applied to any other setup with minor changes.
First, create a database dump in case something goes wrong
docker compose exec mongodb sh -c 'mongodump --archive' > db.dump