Mailbox SP
The Mailbox SP is a device Mario has in Paper Mario: The Thousand-Year Door. It resembles a Game Boy Advance SP and is used to receive e-mails. Although it would make sense that one could send messages with it, it is never shown if it is possible. Mario receives e-mails from X, Princess Peach, and various other people throughout the game, mostly from people who Mario has helped in the Trouble Center, as well as the RDM.
Whenever Mario received e-mails from somebody, the Mailbox SP would ring usually with the theme from Super Mario World that played before a castle was destroyed. If Mario received an e-mail from Peach, it would ring with the title theme from Super Mario World. Whenever Jolene (AKA X) or Grubba sent Mario an e-mail, the ring tone would be the Ice Land theme from Super Mario Bros. 3.