Hello, I'd like to install Postfix on our Debian Linux laptops to handle local system messages / notifications, e.g. from "unattended-upgrades" (like "dnf-automatic" on RH-based Linuxes) or from failed cron jobs.
In our LAN we have an internal Postfix VM (not accessible from the Internet) that accepts any emails on port 25 and rewrites / replaces *any* recipient to a single admin mailbox. We use this Postfix to collect all system messages from other VMs in the LAN. Each of them has Postfix installed, listening on 127.0.0.1 and with relay_host pointing to the central "collector" Postfix VM. I'd like to have the laptops send their local system emails to this central admin mail server, as well. As with the virtual machines, I'd install postfix and set the central mail collector Postfix as relay_host. But the internal admin mail collector server is only accessible if the laptops are connected to our internal LAN or to our VPN (OpenVPN). It has an internal IP address from 10.0.0.0/8 range. This leads to my question: What happens to laptop-locally generated / received emails, if their local Postfix can't reach the relay_host in the intranet? 1) Incoming emails on the laptop-local Postfix are not accepted and lost. 2) Laptop-local postfix will accept all incoming emails, independent of the state of relay_host, and try to deliver them to relay_host infinitely until relay_host can be reached? 3) ...? Possible behavior (2) was what I'd like to achieve. Can this be configured? E.g. the retry interval? Or would you suggest an entirely different approach to collect the local system emails from the laptops? Thank you for your advice! Reg
