This article explains how to remove the spam categorization from emails in Yahoo! Mail

It's easy to move emails out of the spam folder and into the folder where you want it to be.

1. In your Spam folder, open the email that was marked as Spam.
2. Click the Not Spam button.

If you continue seeing these emails in your Spam folder and want them in a Non-Spam folder, you can set up a filter and send them to any folder you wish. For more information, please see our help article explaining how to set up and use filters.

Also, if spam somehow gets into your Inbox, select the spam email by placing a checkmark in the box next to it, and then click the Spam button above your list of emails.