Hi, I had the same observation.
In PVE you have the option to configure the email_from address. Currently it's not implemented in PBS.
So I filed an enhancement request: https://bugzilla.proxmox.com/show_bug.cgi?id=3162
Let's see if it gets accepted and implemented. An let's have patience
Thanks @janssensm for adding an enhancement request! I'm adding my voice to this as well as currently I have no way to receive emails on PBS activities without the ability to change the from address:
In PVE under Datacenter > Options I can change my Email From Address to what I need. This works to allow emails on PVE backups. I think it is a very important item to add to PBS.
Until the feature option can be added to PBS..is there a file or command we can issue from the terminal to update the email from address on PBS? Now that PBS is stable version 1 I'm beginning to rely heavily on PBS for my daily backups and would like to be notified on PBS tasks I have scheduled.
I don't think that's possible.
You probably could configure postfix to solve it but as PVE and PBS use a bit of their own logic around sending of emails, I didn't want to touch that.
As a workaround I decided to tweak my OPNsense for it.
I use OPNsense with postfix plugin as a smarthost, and have configured a sender canonical rewrite there to replace the sender address.