Governs who can view this email in the archive.
ARCHIVE_ONLY is the odd one out: the email is publicly archived but
is not email content at all (e.g. an imported blog post), so it is
excluded from email-rendering contexts like "recent issues" widgets.
This email is visible in the archive to everyone, but is not email content (e.g. an imported blog post) and is never sent or shown in email-rendering contexts.
This email is not visible in the archive.
This email is visible in the archive to everyone.
This email is visible in the archive to paid subscribers only.
This email is visible in the archive to subscribers only.