This solution will also unlock the feeding the dog achievement and love letter achievement.
I did all this which unlocked it. I missed a couple of emails first time through and it didn't pop, so I'm not 100% sure if they count or not, but follow this as follows.
2178 door code of chavez's office
Play the phone message
Read all of her emails
Lab 2A:
play the phone message
Dossier inside a cupboard
Emails on the pc
Casasius F-2 strain under a microscope in the centre of the room
Voice recorder in the locker to the right of the entrance.
Whiteboard at the back of the room
Lab 2E:
Voice recorder under the sink infornt of you
Emails on pc
Notes inside locker in the back of the room
(We'll come back to 2E to progress the story)
Lab 2D -
Pick up love letter in the cupboard of desk
Enails on PC
Phone message
Whiteboard at the back of the desk
Fridge sample on the left hand side of the desk, examine it under nearby microscope
Dossier inside the lab
Benson's office:
Door code 5402
Play phone message on Benson's desk
Read her emails
Interact with chocolates and leave the letter (unlocks seperate achievement)
Dossier in drawer under spots poster at the right hand side of the room
Back to 2E:
Door code 2810
Play ipod in corner
Feed the dog (unlocks seperate achievement)
Calico island poster
Also of note is a plant sample under a microscope which may count towards the achievement in the biolab.