Yahoo has been emptying all the email from the inactive for 4 months accounts, without notification. Is yahoo going to put back them back?...

Right in Yahoo’s TOS it says:

Number 13: “You agree that Yahoo! has no responsibility or liability for the deletion or failure to store any messages and other communications or other Content maintained or transmitted by the Yahoo! Services. You acknowledge that Yahoo! reserves the right to log off accounts that are inactive for an extended period of time.”

and

Number 15: “You agree that Yahoo! may, without prior notice, immediately terminate, limit your access to or suspend your Yahoo! account, any associated email address, and access to the Yahoo! Services. Cause for such termination, limitation of access or suspension shall include, but not be limited to, (a) breaches or violations of the TOS or other incorporated agreements or guidelines, (b)requests by law enforcement or other government agencies, (c) discontinuance or material modification to the Yahoo! Services (or any part thereof), (d) unexpected technical or security issues or problems, (e) extended periods of inactivity, (f) engagement by you in fraudulent or illegal activities, and/or (g) nonpayment of any fees owed by you in connection with the Yahoo! Services. Further, you agree that all terminations, limitations of access and suspensions for cause shall be made in Yahoo!‘s sole discretion and that Yahoo! shall not be liable to you or any third party for any termination of your account, any associated email address, or access to the Yahoo! Services.

Termination of your Yahoo! account includes any or all of the following: (a) removal of access to all or part of the offerings within the Yahoo! Services, (b) deletion of your password and all related information, files and content associated with or inside your account (or any part thereof), and© barring of further use of all or part of the Yahoo! Services.”

Sounds to me like you didn’t use the account for the extended period of time and they terminated it. Considering part of making an account is agreeing to the TOS, it sounds like you are out of luck.

@Seaofclouds thanks so much for that.
By the way, it was a general question, nothing to do with whose account was emptied.