Sometimes legitimate Yahoo e-mails are discovered in spam.

Please perform the following:
  1. Use a web-browser to access https://mail.yahoo.com. 
  1. Login to your account.
  1. Open the SPAM mailbox
  1. Select our e-mail and then choose Not Spam (as shown above)

  2. Next open your Yahoo contacts (in the same web-portal)
  1. Click on ADD CONTACT and add the e-mail address in question. This will ensure these e-mails will no longer be marked as spam.