- Plesk for Windows
- In Plesk Onyx, the mail forwarding option Mail for Non-Existent Users for Selected Domains > Redirect to an external mail server with the IP address is not available
- SmarterMail 15 is used as a mail server
This is a bug in Plesk with ID #PPPM-8137. It will be fixed in future Plesk releases.
As a workaround, configure the option manually directly in SmarterMail: