+=head1 LABELS
+
+Labels are user-defined values analogous to IMAP/JMAP mailbox
+names. They must only contain lowercase characters, digits, and
+a limited amount of punctuation (e.g. C<.>, C<->, C<@>).
+
+Messages may have multiple labels.
+
+=head1 KEYWORDS
+
+Keywords are "flags" in Maildir and IMAP terminology.
+Common keywords include: C<seen>, C<answered>, C<flagged>, and
+C<draft>, though C<forwarded>, C<phishing>, C<junk>, and C<notjunk>
+are also supported.
+
+When writing to various mboxes, the common keywords will be
+mapped to the C<Status> and C<X-Status> headers.
+
+Messages may have multiple keywords.
+