Currently, failed tests can only send an email to either the submitter or the mailing list. We need to send it to both targets.
In general, the patchwork should send an email to the original submitter (to) and 'cc' the mailing list and possible those 'cc' included by the submitter.
"Mail recipient" can be configured to option "Mailing List" in Django's Site Administration > Tests > patchtest view. This produces email notifications to all of patch Submitter, recipients in "Mail to List" and "Mail cc List" fields, and the layer's mailing list itself (for example, openembedded-devel@lists.openembedded.org).