If you find a 'good' email in your message quarantine then you can whitelist the sender directly from the quarantine by clicking on the link that says 'approve/whitelist sender'.
Here's how to whitelist a sender's email address or domain:
By default you'll be shown the Approved tab, which lists email addresses and domains that we should always accept mail from without filtering.
You'll be presented with a dialog box with a large text entry field where you can list the email addresses and domains that you want to whitelist.
Changes to your whitelisted sender list will normally take effect within 60 seconds.