Ymail is known to be a possible ending domain of an email address that is created on Yahoo mail. If this would be checked, the interface will be the same. This has been opened up to people before because people would like to create addresses that they want, but the ones that they wish to are not available anymore.
Aside from Ymail, rocketmail is another domain that was opened up by Yahoo, especially during the time that it was extremely popular. Yahoo.com is a website that comes with details and information that you may need. You can check it out to search for information that you need. This is still one of the search engine sites that people like to check.