Email Whitelist

You’ve seen it in your email messages, but do you know what it means when someone asks you to “whitelist” them? Well, in a nutshell, they are requesting that you add them to your contact list. Wikiipedia describes it this way:

An e-mail whitelist is a list of contacts that the user deems are acceptable to receive email from and should not be sent to the trash folder.

Spam filters that come with e-mail clients have both whitelists and blacklists of senders and keywords to look for in e-mails. If a spam filter keeps a whitelist, mail from the listed e-mail addresses, domains, and/or IP address will always be allowed.

Some internet service providers have whitelists that they use to filter e-mail to be delivered to their customers. ISPs receive requests from legitimate companies to add them to the ISP whitelist of companies. Companies either pay for a time period to be allowed to e-mail their customers or the companies pay per complaint received by the ISP from their customers. These payments per complaint increase incrementally; i.e., the first 10 complaints are $10 each, then the next 10 are $20 each. These funds are then used by the ISPs to fund anti-spam programs to prevent unwanted e-mail.[citation needed]

If a whitelist is exclusive, only e-mail from those on the whitelist will get through. If it is not exclusive, it prevents e-mail from being deleted or sent to the junk mail folder by the spam filter. Usually, only end-users would set a spam filter to delete all e-mails from sources not on the whitelist, not internet service providers or e-mail services.

Using whitelists and blacklists can assist in blocking unwanted messages and allowing wanted messages to get through, but they are not perfect. E-mail whitelists are used to reduce the incidence of false positives, often based on the assumption that most legitimate mail will be from a relatively small and fixed set of senders. To block a high percentage of spam, e-mail filters have to be continuously updated as e-mail spam senders create new email addresses to e-mail from or new keywords to use in their e-mail which allows the e-mail to slip through.


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