Recent industry studies have shown that as much as 90% of all email is spam, and as many as 5% of legitimate email messages do not reach their recipients. As a result of the growing problem of spam, spam filters have now become much more aggressive.

Although there are many reasons for legitimate messages not reaching their recipients, spam filter 'false-positives' are widely cited as the leading cause. Although spam filters are typically very accurate in correctly identifying and filtering junk messages, spam filters are often prone to erroneously filtering messages that are not spam. These messages are often sent to a junk mail folder (or discarded altogether) without any notice to the sender or the recipient.


Related:
Blacklists, Greylists, IP Reputation, and Spam Filters
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