## How do I search for punctuation, specific special characters, or regexp?
Please see the [[notmuch-search-terms manual
-page|manpages/notmuch-search-terms-7]] first,
+page|manpages/notmuch-search-terms-7]] first.
The main thing to understand is that Xapian, and therefore Notmuch, searches are
closer to natural language searches than regular expression
The boolean prefix searches (see Boolean and Probabilistic Prefixes in the man
page), such as tag: or path: searches, need an exact match.
+
+## How do I search for the `List-Id:` header?
+
+Currently there is no way to search for `List-Id:`. As a workaround, try using a
+`to:` prefix search (which covers both `To:` and `Cc:` headers) on the mailing
+list address.
+
+Limitations in the duplicate message handling are the main reason for not
+indexing the `List-Id:` header. If you receive the same message via both the
+list and directly (by way of `To:` or `Cc:`), only the first message encountered
+will be indexed. Only the message received via the list will have `List-Id:`,
+but you would expect a `List-Id:` search to find the message, regardless of the
+order in which the duplicates were received. This is a more general problem than
+just `List-Id:`, and once this has been resolved, adding `List-Id:` indexing is
+trivial.