Sender ID
A Microsoft-led sender authentication method from 2006 that checked an SPF-style record against a header address; its RFCs are now Historic.
What it means
Sender ID, published as experimental RFC 4406 with the Purported Responsible Address algorithm in RFC 4407, applied SPF-style records to an address taken from the message headers (usually Sender or From) rather than the SMTP envelope. It used spf2.0 records, or reinterpreted v=spf1 records, which caused conflicts with SPF.
The IETF reviewed both experiments in RFC 6686 (2012) and found SPF far more widely deployed; Sender ID's RFCs were later moved to Historic status. Header-based authentication was taken up by DMARC instead.
The name survives in one Outlook.com rejection, "Sender ID validation failure", sent when the domain's record authorizes no senders, such as v=spf1 -all.
Related terms
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Sources
What this definition rests on. The wording is ours; the facts are theirs.
All 432 terms in the glossaryThe wiki: blocklists and bounce codes