As a general rule, no. You can't use an email address as your Yahoo! ID. Until recently, we would ignore the "@" symbols when people would enter them in a Yahoo! ID field during registration and login. We no longer ignore these characters.

If you have been logging in as "user@isp.com," your Yahoo! ID is probably "userisp.com." Try logging in without the "@" sign.

Exception for partner domains: Yahoo! now has relationships with some partners where the Yahoo! ID is an email address in a domain belonging to a partner. For example, Yahoo!7 customers have "Yahoo!7 Yahoo! IDs" ending in "@yahoo.com" that they need to type at login.