How to enable my services to send emails from my top-level-domain instead of subdomains?

What type of hardware are you using: VPS bought online
What YunoHost version are you running: 12.1.25
How are you able to access your server: The webadmin
SSH

Describe your issue

When installing a service which wants to send emails on a subdomain (e.g. app.yunohost.org), Yunohost assigns it a mail address on this subdomain (e.g. web@app.yunohost.org).

This poses deliverability challenges, since these subdomains don’t normally have mail-specific DNS records (MX, SPF, DKIM). You could of course add them for each subdomain, but this is tedious and IMO unnecessarily redundant. I would much rather have the services all use mails on the top-domain (e.g. webapp@yunohost.org).

Is this possible? In my case I tried to manually override the service mail for Outline Wiki, but I got the error: “Sender address rejected: not owned by user”.

Can I configure postfix to allow this for all services?

Thank you in advance!

Share relevant logs or error messages

Sender address rejected: not owned by user