Microsoft is introducing a dark mode to the company’s Outlook.com web mail service today. The software maker previously teased the dark mode earlier this month, and previously introduced a temporary version for Halloween last year. This new permanent dark mode can be enabled from the quick settings toggle, and only currently works with the default blue theme. It’s a lot more refined than the Halloween mode, with more of a grey appearance than black.

“One of the most crucial principles we had when designing Dark Mode was to minimize the amount of eye strain that people felt,” explains Microsoft. “Many email clients on the web today advertise a dark mode, but we learned from interviews with others and our own usage that having the reading pane be on-light while the rest of the interface was left on-dark often made the experience worse than if the full screen were left on-light.”

There’s a toggle to switch from black to white backgrounds in emails

The dark mode for Outlook.com is one of the most highly requested features for Microsoft’s web mail service, and the company says it tuned the Halloween prototype to redesign the colors and code “multiple times” before releasing it today. Microsoft has even included a toggle within the body of emails so you can disable the dark mode if a message is difficult to read.

Microsoft hasn’t implemented the new dark mode as a theme, and the company says it imagines “that there would be a dark experience for all available themes in the future.” Outlook.com is now used by more than 400 million active users, and Microsoft recently launched a new design and features for the calendar and contacts sections. This new design is coming out of the beta phase today, alongside the dark mode addition.