subject

How can i change the subject in my old emails in yahoo acc?

Well, you can’t really, as far as I know. The Microsoft Outlook email client is able to do this, but as I recall none of the free clients can -- and none of the webmail that I'm familiar with. If you only have a few emails that you want the subject changed for, you could simply forward them to yourself and change the subject before sending. But if you have a lot of emails you want altered, that wouldn’t be very practical. Others here may have ideas, but this is all I can offer. Sorry. :-(