# What is Spam Filtering?

> Spam filtering is the automated evaluation of email to identify unsolicited, unwanted, or abusive messaging and decide whether to reject, defer, quarantine, label, route, or deliver it.

- Canonical URL: https://yellowcube.eu/glossary/spam-filtering/
- Publisher: Yellow Cube
- Language: en
- Contact: hello@yellowcube.eu

## Content

Filters can act during mail transfer or after receipt and may combine sender and infrastructure reputation, volume patterns, authentication results, message content, links, attachments, recipient feedback, and campaign relationships.

Whether a message is unwanted can depend on consent, subscription state, local policy, and recipient context. Layered signals, transparent quarantine and appeal paths, user reporting, and measured tuning help operators reduce disruption while responding to changing senders and evasion techniques.

### Key points

- **Signals and actions:** Combine connection, sender, authentication, behavioral, content, and recipient-specific evidence; choose proportionate actions and avoid relying on one score or blocklist.
- **Operations:** Monitor delivery and complaint patterns, expire stale rules, review quarantines, protect high-risk mailboxes, and provide safe mechanisms to report, release, or permanently block messages.
- **Privacy and usability:** Limit collection and retention of message data, restrict analyst access, explain user-visible labels, and account for legitimate bulk, transactional, emergency, and accessibility-related mail.
- **Important limitation:** Every filter has false positives and false negatives, and adversaries adapt to detection. Authentication can support a decision but does not make a message wanted or benign; filtering also cannot eliminate all deceptive interaction.

### Related terms

[Email security](<https://yellowcube.eu/glossary/email-security/>) · [Phishing](<https://yellowcube.eu/glossary/phishing/>) · [Content filtering](<https://yellowcube.eu/glossary/content-filtering/>) · [Domain-based Message Authentication, Reporting, and Conformance (DMARC)](<https://yellowcube.eu/glossary/domain-based-message-authentication-reporting-and-conformance/>) · [Email spoofing](<https://yellowcube.eu/glossary/email-spoofing/>)

### Sources

[NIST CSRC Glossary, Spam](https://csrc.nist.gov/glossary/term/spam) · [NIST SP 800-177 Rev. 1, Trustworthy Email](https://csrc.nist.gov/pubs/sp/800/177/r1/final) · [RFC 2505, Anti-Spam Recommendations for SMTP MTAs](https://www.rfc-editor.org/info/rfc2505/)

## Attribution and scope

This Markdown representation is generated from the same approved content records as the canonical HTML page. Cite the canonical URL above when referencing this material. Product and service descriptions are informational; confirm project-specific requirements with Yellow Cube.