Hi! Sorry, I didn't managed to do in-game tutorial in time. But I made a tutorial on the game page
Summary: read mail, if you think it's spam message hit flag, if it's work mail - forward(arrow) to "filtered mail". Some mails can be forwarded to other chats, but it's stated in-game.
Also you have energy meter - just get your mouse on cat and it will be shown(may be buggy in web version, but still must work). While doing mails it will decrease. Go to sleep or order some food to regain it. Also you have a certain number of mails you have to do before going to sleep: also point on a cat to see it
Sorry again, maybe fix this after gamejam(I just realized I need a tutorial 15 min before deadline)