https://commoncomputerproblems.net/spam-filtering-101/

In order to keep pace with spammers, errs are frequently changed.

If spammers alter their email address. It could trick the systemand penetrate the spam filtering system prior to being officially identified as spam. To guard their operations firms, they often set up separate blocklist filtering. In particular, they could prevent headhunters from poaching the employees they have trained. The emails that waste on time and effort for employees can be blocked by them, including special offers emails. The content filtering system analyzes each email’s contents and uses this information to determine whether it’s spam.

Since spam email content is known, the filters work well. They typically promote simple content, offering offers and focusing on human emotion like fear or desire. These spammers use target phrases such as discounts and offers for the purpose of triggering the filter. Companies may use filtering of content to look over emails for improper language, blocking them accordingly.
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