The location in the Fastmail web UI is a bit weird, but this kind of "What's New" tray is the correct way to handle changes to your website or app, maybe with a "Show me" action for more details.

Please don't throw a boatload of "We just changed our UI we're so excited BLA BLA BLA" pop-ups in my way if I haven't used your product in a while.

A Fastmail "What's new" notifications feed showing various recently launched features of the Fastmail service.
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