Use the Interface Details table in the Email MTA Configuration page to delete the SMTP (pether3) interface configuration using the Web UI.
To delete the SMTP interface configuration:
In the Web UI, choose Settings > Email MTA.
In the Interface Details section, locate the IPv4 address or IPv6 address you want to delete.
Click the Delete (trash can) icon.
Click YES.
The interface is deleted from the SMTP configuration.