Add multiple email addresses to the "Forward to address" list
Is it currently possible to set only one mailbox to forward the mail for non-existent users in Domains > example.com > Mail > Mail Settings > Forward to address.
Please allow to add more than one email address for this setting.
Plesk Tech Support shared this idea
This request did not become popular, we must decline it. But there is an easy workaround: Simply forward the mails internally and setup the forwarding list from that internal mail address.