*Obtain this achievement as early as possible to avoid missing it*
At a certain point in the game, you’ll be told that you have new emails waiting for you. Exit the Animus, and head towards Altair’s statue. Press any button to access your computer and the achievement will unlock.
Be sure that you check your email before the final memory sequence. After completing the final memory sequence, you cannot exit the Animus (not even replaying DNA). If, for some reason, you do miss this achievement, don't be too stressed out. The email can be checked as early as sequence 2, so just start a new game on another save file if that happens.
Ok what you do, After you and the others have relocated the animus under ground in monteriggioni leave the animus and walk pass Shawn (or whatever his name is) and find the empty computer and press B (interact) and you should get it.
emails were a bit interesting. There seems to be a bit of a love thing going on between Rebecca and Shaun. Lucy is communicating with someone named William, higher-up in the Assassins, who tells her not to get too attached to Desmond.
Just FYI on this one you can get it without being told that you have emails. I got it just for logging in to check but no emails in my inbox or anything - but I couldn't look at the emails to or from the other characters so if you want that then wait till you're told about it.