List-Id
A header field (RFC 2919) that gives a mailing list a stable identifier shaped like a domain name, so mail programs and filters can recognise mail from that list.
What it means
The value is an optional description followed by an identifier in angle brackets, built from a label and a domain the list owner controls, as in List-Id: Product updates <updates.example.com>. The identifier is meant to stay the same when the list moves to other software or another host, unlike its posting address.
Mail programs and readers filter on it, and RFC 3834 allows automatic responders to ignore messages carrying List- fields, which keeps out-of-office replies away from list mail. A sender with several streams, such as a newsletter and product updates, can give each its own List-Id so readers can tell them apart in their rules.
Example
List-Id: Product updates <updates.example.com>Related terms
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