Trusted email addresses, domains, and even IP addresses can be whitelisted or in other words, stored in a database for future connections. Only emails from a whitelisted source will be delivered to the user’s inbox. This method is actually great to eliminate spam emails.
The problem is it can produce false positives. This means emails that come from legitimate sources may be undelivered. To deal with this problem, a challenge-response technique can be implemented. This works by responding to the emails that come from unknown senders.
The system will send a challenge back to the sender where the sender is required to answer certain questions. This challenge may be in the form of an image that displays a series of letters and numbers that can only be deciphered by a real human.
This means to determine whether an email is legitimate, the challenge-response method will use a combination of human judgment and software technology. If the sender can give correct answers, his or her email will be allowed to go through the system to the inbox.
However, if this spam protection method is really implemented like this, some problems will appear. Although spammers are more likely to disregard such challenges, this may also discourage legitimate email senders from following through.
- How to reduce the amount of spam in your mailbox by 95% or more.
- In case you provider does not provide adequate spam filtering.
Tags: challenge-response, whitelist, whitelisting