Stupid question, I know. But I cannot get past the first locked door because of this.
I can select the email in the inventory menu, but no matter what I do, nothing happens.

you don't - not implemented yet.

so, how do I get the code to open the door?

Its written on the left side of the keypad.

Look for the BLOOD! Not a stupid question... I had the same problem... Took me about 15 mins before I saw it :)

If it's the very first door make sure you look around carefully, pick up all items and open the crates!

Oh man, it's like when you try to hack your brother's computer and try to find what the password is while it's written on a sticky note on his monitor :D

BTW this door is more than easy to pass, you'll come back here when you'll have to pass the lift behind that door ;D

Doh! Damn my assumptions anyway. :)