Can I change the Subject line on received emails?

A company sends me emails that I need to save. I would prefer to change the subject line to make it more useful to me. Other than forwarding every email to myself with my customized subject line and then deleting their original email, is there a way to change the subject line on the email they sent me and save it... show more A company sends me emails that I need to save. I would prefer to change the subject line to make it more useful to me. Other than forwarding every email to myself with my customized subject line and then deleting their original email, is there a way to change the subject line on the email they sent me and save it with that new info? I know I can delete an existing subject line and replace it in Outlook. Can I do that in Yahoo mail?
Update: Thanks for the quick reply, Froggie!
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