It does some UDP fuckery to bypass NAT and firewalls
I wouldn't be surprised if they use hole punching. It's an old but effective technique which Skype famously used back in its heyday.
fragrantvegetable
joined 2 years ago
I've been using them for a bit over a year now and don't have any complaints so far. If you don't care about the office suite, their email only package is €1.50/month for 5 users, which is hard to beat. You can use your own domain too. I like that their web/android clients have a proper conversation view that also shows your replies (like Gmail does). This has been missing from other providers I've tried (except Fastmail). Their android app is on F-Droid and open source which is nice. There were a few odd translations, like "Transfer" instead of "Forward", but I think they've fixed those since. It's not been long enough for me to comment on reliability or missing emails, but so far so good.
I'm in the same boat, but I've pretty much decided to move my Restic backups to Hetzner Storage, unless something better comes along before I do the migration.