Whenever I open OS X Terminal, it says "you have mail". Why is this, and how can I get rid of this message?
OS X machines, just like Linux and Unix machines, have the capability to send emails to other machines, as well as receive emails from other machines directly to and from your local machine's user account. Long story short, if you are seeing the "you have mail" message in your Terminal window, your computer's local SMTP server has somehow received an email message to your account. (For far more details, look at the references below, or Google the terms "postfix", "sendmail", and "OS X").
Solution (using Terminal only):
This solution solely uses the Terminal. If you are not comfortable with this, please do not follow the rest of this how-to as you can cause some serious damage to your system if you don't know what you're doing. If you'd still like to poke around your system, try the "partially without Terminal" solution below.
The mail received in your account is saved in the file "/var/mail/$USER", where $USER is the name of your account. For instance, if your account was named "someone", and if your home folder shows up in the OS X filesystem as "/Users/someone", then the mail on your machine has been stored in "/var/mail/someone".
Because this is a regular text file, you can simply open it in a text editor to read the mail stored in this file, or you can view the file's contents directly in the Terminal with the command "more /var/mail/$USER", replacing "$USER" with your username (although typing in the command exactly will also suffice in this case, as Terminal will replace $USER with your username).
To get rid of the "you have mail" message, simply move or delete the email file from /var/mail. For instance, assuming again that your account name is "someone", you can type into the terminal "sudo rm -i /var/mail/someone", then confirm deletion when prompted. This command is permanent and possibly destructive if done wrong, so do not make any typos.
Finally, if you have reason to believe that something unusual is sending out emails from your machine after looking at your email file in /var/mail, you can check out the mail log on your machine with the command "more /var/log/mail.log" to see what email activity has occurred on your machine.
Solution (partially without Terminal):
To view the local mail folder on your OS X system in the Finder, type the following command into the Terminal window:
Once open in the finder, to view the mail on your local machine, open the text file that matches your user in the "/var/mail" folder. For instance, if your username is "someone" and your home folder is "/Users/someone", then the email file to open is "/var/mail/someone".
With the OS X Finder still open to the "/var/mail" folder, in order to remove the "you have mail" message from the Terminal move the email text file from the "/var/mail" folder, or delete it altogether. For instance, if your user is "someone", you will want to either move or delete the file "/var/mail/someone".
After reading your email, if you suspect that there is unusual email activity happening on your local machine, you can confirm this by looking at the machine's email log with the following Terminal command: