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These requirements sound very similar to something like LoRa, would be worth checking out stuff in that space too.

You could quite viably fetch the latest article from an RSS feed in this space, or reply to an email, even with minimal compression. The less technical the solution is the better.

I would definitely suggest to have some commands built in and have the ability to poll the current state of your service to ensure it's not being abused, etc. You also might need a human the other side to reboot it occasionally, so make it very simple to get back online.