Use case of keywords in mails

Salut
Since 4D 17R5 it becomes possible to add keywords in a mail header:
<code 4D>
C_OBJECT($O_Keywords)
$O_Keywords:=New object(“Matrafich”;True;“Gottseidank”;True;“keywordnotinserted”;False)
$email.keywords:=$O_Keywords

</code 4D>

In the real life, who, when and where uses keywords?

For example: Spam application add their keywords to tell if a mail is (likely) a spam or not.
Some application add Keywords to tell this mail is made by this application, etc.

Bon.

et quand utiliser ces variables préfixées en $ quand j’envoie un message:

<code 4D>
C_OBJECT($O_Keywords)
$O_Keywords:=New object
$O_Keywords["$id"]:=True
$O_Keywords["$accountId"]:=True
$O_Keywords["$subject"]:=True
$O_Keywords["$answered"]:=True
$O_Keywords["$forwarded"]:=True
$O_Keywords["$seen"]:=True
$O_Keywords["$flagged"]:=True
$O_Keywords["$hasAttachments"]:=True
$O_Keywords["$lastMessageSentAt"]:=True
$O_Keywords["$excerpt"]:=True
$O_Keywords["$messageCount"]:=True
$O_Keywords["$photoBlobId"]:=True
$O_Keywords.Matrafich:=True
$O_Keywords.Gottseidank:=True
$O_Keywords.keywordnotinserted:=False

// EOM
</code 4D>