There are many chances you would lose your yahoo mail / messenger passwords and would not be able to recover it. Here are some of the steps you need to perform.
The basic and normal procedure for recoving your password is to start with this page where you will be asked with your Yahoo ID and will need to confirm whether you have used credit card previously with this login, because if you would have used a credit card previously your account will be verified with those CC details without any charges. The next step would entering your identity details which you would have submitted while registering this yahoo account like Birthday, ZIP (or Postal) Code, and Country.
REQUEST A NEW PASSWORD:
If the above information did not assist you, please attempt to request a new password. Remember that our team may not reset your password or remind you of your current password.
To request a new password:
1. Click on the MY ACCOUNT link at the top of the Yahoo! home page.
2. Enter your password.
3. On the Account Information page, click on the CHANGE PASSWORD link.
You will be prompted to change your password to something different. It is recommended your new password not contain any part of your old one, for security reasons. If you have followed the directions above, and are still unable to obtain a new password for your account or feel that your account may have been compromised, please reply to this email with the following information you supplied during your Yahoo! registration.
* Yahoo! ID (If you cannot supply this ID, please give your alternate
email address given during your original registration)
* Your name
* Date of birth (mm-dd-yr)
* Your alternate email address
* Secret Question and Answer
* Your city and state
* Zip Code or Postal code you entered during registration
* Your country
If the above solution does not work out , you may have to lose the email because the normally sold softwares which are used for recovering the password are all fraud and they cannot help you to recover the password. All these Yahoo Password Recovery Softwares are fake because none of these can recover the password from yahoo so dont ever buy them.