The Problem
When you delete a message, and the time for it to be automatically marked as ‘read’ hasn’t expired (e.g. 2 seconds), it’s moved to the trash folder but is still set to ‘unread’. To remove the unread count for the trash folder, you have to manually go in there and mark all messages as ‘read’. Apparently this also happens for spam messages.
Proposed Solution
A new option in the settings that allows you to “Automatically mark deleted & spam messages as ‘read’.” With this enabled, deleting a message would automatically mark it as ‘read’ as well as moving it to the trash folder. Same with spam.
Alternative Solutions
Manually marking messages in the trash as ‘read’ (tedious and a waste of time).
Context
I wanted this ability, and found this other topic for it: Mark trashed and spam messages automatically as read (I guess they didn’t get around to filing a feature request though).