From header if domain is not oursTransactional mail servers will reject sending mails on behalf of third-party domains that are not owned (neither configured) by us.
This happens when someone replies to an Odoo sent mail: Odoo tries to notify followers by re-sending the mail received with the original From header.
eg:
In order to avoid those rejects, we’ll install a module that will check if the domain is in a white list and if not, it will replace the header to a configured email address.
The module mail_outbound_static checks, when sending an email, if the From domain is in an allowed list and, if not, it will replace the From header with a predefined value.