There is not a one-to-one correspondence between items in my inbox and items on my todo list, and items in inbox don't necessarily say what I need to do.

e.g. an e-mail in my inbox asking me to clean the frobulator might translate to one of the following todo lists:

a) 1. clean the frobulator

b) 1. buy frobulator cleaning fluid 2. empty the frobulator 3. clean the frobulator 4. refill the frobulator 5. reply to sender informing them that the frobulator is now clean

c) 1. reply to sender telling them why I can't/won't clean the frobulator

d) (no action necessary)

But my inbox won't help me remember which of these is the case. And that's ok, because that's not what it's for. That's what my todo list is for.