If you don't have a Ybb mail address. you can create an email id from here then you can Ybb email login.
Open opera mail Software App. Click on Mail and Chat Accounts.... Select Email and click Next
Enter Your Real Name. Then Enter Email Address. Then Click on Next.
Enter Email Address as Login name and Enter Password in Password. Check Mark IMAP. Then Click on Next.
Enter imap.mail.yahoo.co.jp in incoming server settings. select SSL/TLS Enter apple.smtp.mail.yahoo.co.jp in outgoing server settings. select SSL/TLS
Then Click Finish
Tap on Done. Now you are ready to use your Ybb email account on your opera mail.