Those warnings require you to actually be in the game to be able to see them. That level of notification is not enough imho.
Real life will (or at least should) take priority over a game, so in those instances where people have had to be away and genuinely forget to refuel, they shouldn’t be punished for that.
You’re also more likely to regain players that have become inactive for whatever reason, when you notify them that all their building efforts so far are going to be lost. In not notifying them, you’re more likely to push those people away to never return. I’m not delusional to the fact that some may just log in, refuel and disappear again for 12 weeks (there’s absolutely nothing to stop them doing that now), but I think not having this mechanic, or similar, will do more harm than good.
In all honesty… running a dedicated mail server is a very minimal cost. I run mine for about $10/month. Now, I have no idea of what operational budget the devs have, but I’m not about to try and make monetary decisions for them and to be quite frank, neither should anyone else - that is something that is well outside of our remit as early access gamers.
As I briefly mentioned in another post, it doesn’t even need to be an email. An integration with Discord (and the equivalent on PlayStation(?)) would be sufficient - it’s essentially a free service. As long as you have joined the official discord, the game would be able to private message you about your beacon statuses.
The devs have already expressed an interest into looking at the possibility of integrating the voice coms of Discord into the game… using private messaging wouldn’t be too far of a stretch from there.