Maily needs Google Chrome, and your Gmail address on its tester list. Paste one line below, then follow the questions. Updates install on their own after that.
curl -fsSL https://maily.rushour0.com/install.sh | bash
irm https://maily.rushour0.com/install.ps1 | iex
Mac: curl -fsSL https://maily.rushour0.com/install.sh | bash -s -- --uninstall
Windows: & ([scriptblock]::Create((irm https://maily.rushour0.com/install.ps1))) -Uninstall
Then click Remove on Maily's card in chrome://extensions.