Step 6 Whitelist/Blacklist
Anti-Spam Filter Setup Guide | DoIT

Whitelisting is to place an e-mail address or domain on a list of items that is deemed spam- or virus-free, meaning if you whitelist an e-mail address jack@jack.com & a domain nl.edu you will always receive e-mail from Jack & everybody from nl.edu organization regardless of the content of the e-mail. If you add somebody to your whitelist please make sure that you absolutely trust that person. Generally adding an entire domain is not a good idea unless deemed necessary.

Blacklisting is exactly the opposite for Whiltelisting. You will not receive an e-mail from the person or a domain that is blacklisted.

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