This isn't exactly a Show HN as in "I made this", but more like "Hey, you should know about this".
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If you dislike new Gmail's interface, but don't want to go back to the really primitive old one, you can install Roundcube on your server, and log into Gmail with it. It has a really nice UI that's responsive (looks like this: https://i.imgur.com/7QMBMxc.png ), and it's quite a nice software in full. It's easy to setup and it sends and receives emails over IMAP and SMTP.
Roundcube: https://roundcube.net/
If you're interested in how to set it up, you can comment, I'll write a post on my blog soon if there's interest...