What’s the difference between block, quarantine, and junk classification?
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Block means the message is rejected during the SMTP transaction. It never enters the mail system. The sender receives a bounce notification. This is the most severe action, typically reserved for known threats or blacklisted senders.
Quarantine accepts the message but holds it for administrator review, common in enterprise environments. The recipient may not see the message unless an admin releases it. Quarantine is used when the filter is uncertain and wants human judgment.
Junk or spam classification delivers the message to the recipient's spam folder. The message is accessible but segregated from the primary inbox. Users can rescue messages from junk, which trains the filter to adjust its judgment.
The progression represents decreasing severity: block is total rejection, quarantine is supervised holding, and junk is delivery with a warning label.
Blocked ships are turned away at sea. Quarantined ships anchor under guard. Junked ships dock at a separate pier where the crew must come retrieve their cargo.
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