PlanetsCentral

Read and unread messages differ only with a purple outline, it's not easy to discover.

Ah, I see.

You're not the first to notice, but so far I didn't have an idea how to improve that. Also, whether the glow is prominently visible probably depends on your display type and settings.

On the other hand, the idea with an open envelope makes a lot of sense and I wonder why I didn't think of that. Let's see. (I would opt against the checkmark, because that clashes with the "replied" arrow.)

--Stefan