FOR GMAIL
Add their email addresses to your Contacts list OR create a filter so the messages are never sent to Spam.
FOR YAHOO
- Check your Spam folder: Periodically check your Spam folder to ensure that you do not miss a message. You can move a message from the Spam folder to your Inbox: Check the checkbox beside the message and select the Not Spam button.
- Add senders to your Contact list: Adding someone to your Contact list ensures their messages won't end up in your Spam folder.