I just did this last week. I originally tried stalwart as that seemed to be a pretty small footprint (1 docker container) and had built-in PGP support. But I couldn't get the built in acme bot to work with my dns provider, maybe you'll have better luck.

I then tried mailcow and had e-mail flowing in under an hour. Of note, there are a lot of containers if you go the docker route, some may not be necessary if you just want email. I have so far left the default containers running as I don't really care about the extra containers, it's all running on a vm w 5 GB of RAM. I'm not concerned about PGP at this point as the server hard disk is encrypted via LUKs.

I can't speak to your first 2 questions, dovecot comes with mailcow, but I didn't have to set any specific settings for it.

I port forward directly to the vm, but it's on it's own isolated VLAN. use 993 for imap instead of 143, it requires SSL if using a proper mail server.

I use thunderbird for desktop and fairmail for android. mailcow dockerized does come with it's own webclient SoGo, which didn't seem too bad if that's what you prefer.

I hope this helps!

You can use your own pgp keys w mailbox. And 3rd party email clients. IMO that's the best of both worlds for the available providers that support pgp.

You can use your own pgp keys w mailbox.

Can you use these with a NUT server? I've been unable to find that info. It looks like they have ones with batteries, which makes them a sort of UPS as well, but would be nice to be able to gracefully shut stuff down when the power fails too.

You would be correct, in my case the box itself locks up. meaning my internet from the isp is still working, but no internet inside the house. so a reboot of the device is required.

I already run homeassistant, that's def something to look into. Thanks!

That's not a bad idea, I def didn't think of that lol. Thanks!

I will give this a shot. it hasn't happened in a couple weeks, So I can't remember if the device freezes completely or an interface reboot would do the trick.

I'm thinking this is probably my best option if I can get past the using cloud service issue in my head lol.

I do recall seeing the keepconnect a while ago, but completely forgot about it. will definitely look into this! I guess the main issue I see is that it uses a cloud service, what happens when that service goes offline permanently?

I am looking into why it locks up, that's a fair point. good read, and useful tips. Thanks!

which is what the original question is about...what people are using for backup/emergency internet.

Edit:that probably wasn't clear