Niko Bellic, Johnny Klebitz and Luis Fernando Lopez can all access the site from any computer in the game. The player only gets active emails from people after completion of the mission, Logging On. It is based on Gmail.
The e-mails can be from friends, Niko's mother, or other family members of the protagonist. E-mails can start missions, or they can just be random spam. Most e-mails throught the games are a means of communication, to add detail to important parts of the storyline or reveal information about other characters. The player cannot reply by typing themselves though through either replying using the positively or negatively button to e-mails from other characters (these choices do not affect the storyline). There is only a delete option for spam, however. Selecting emails that have been replied to only have the delete option, unless it is for an Exotic Export car theft missions (in which case the car must be successfully stolen and the mission successfully completed). Read emails will be marked as read when you browse through them.