Can I mark an email as read on the Apple Watch? After I receive an email, I can preview it easily from the notification. If it's just an email I don't need to react, my workflow is to just leave it there as read. However, I can't seem to figure out how to mark an email as read on the Apple Watch, so now I have to dismiss the notification, take out my phone, force touch the email and mark as read.

The option on the bottom of the notification are ’Reply’, ‘Flag’, ‘Delete’, ‘Mark as unread’ and ‘Dismiss’. What is the difference between ‘Mark as unread’ and ‘Dismiss’, since both leave the message as unread. Shouldn't ‘Mark as unread’ be ‘Mark as read’ instead?
When you've previewed the email, that's marked it as read. Therefore the option is to undo this action and mark it unread. If you just want to leave it read after you've previewed it, close the notification and it'll be read.