E-mail is a vital element in society, enhancing communications, productivity and e-commerce. Unfortunately,spammers and online criminals exploit e-mail, creating security, and personal identity threats. Left unchecked,these dangers threaten customer trust and online confidence, as well as the deliverability of legitimate e-mail.
To address this critical security issue, an industry consortium has jointly developed the Sender ID Framework(SIDF), now approved by the Internet Engineering Task Force to help increase the detection of deceptive e-mail,while improving the deliverability of legitimate e-mail. SIDF is an e-mail authentication protocol designed to beimplemented at no cost for all senders, independent of their e-mail architecture. Today, SIDF is the leadingsolution now embraced by over 12 million domain holders, sending nearly 50% of all legitimate e-mail worldwide.
When e-mail-receiving networks include the SIDF results with their existing anti-spam solutions, SIDF canimprove e-mail deliverability while reducing false positives. Although this will not stop spam, SIDF along with theapplication of reputation data, anti-spam and phishing heuristics, will help improve online trust and confidence.
How Does Sender ID Work?
E-mail senders and domain owners need to publish or declare all of the Internet Protocol (IP) addresses of theiroutbound e-mail servers, or IPs authorized to send e-mail on their behalf in the Domain Name System (DNS).These IPs are included in a Sender Policy Framework (SPF) text file.

- Sender or user sends e-mail from their e-mail client of web interface. No interaction or changes to theirclient or MTA are required.
- Recipient’s inbound e-mailserver receives the e-mailand using SIDF, calls thePurported ResponsibleDomain’s (PRA) DNS forthe SPF record.
- The Receiving MailTransfer Agent (MTA)determines if the outbounde-mail server’s IP addressmatches the IP addressesthat are authorized to send e-mail for the domain.
- For most Domain and / or IP sender reputation data is applied to the SIDF verdict check/
- Based on the SPF record syntax, pass or fail verdict, reputation data and content filtering score, thereceiving MTA delivers the email to either the inbox, junk/bulk or quarantine folder. For e-mail whichfails, receiving networks may block, delete or junk the e-mail.
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