• Mail can be read anywhere in the game via the Mail panel. This can be accessed using the Z key or using the Mail icon located underneath the chat panel.
• Items and Palladium can only be attached or removed from mail while the character is in a Station.
• Mail can be sent to any player whose name is known, regardless of whether they are online or not. You can only send mail to one character at a time or to your entire guild.
• Mail is only stored for a certain amount of time. The mail panel shows how long each message has left before it is automatically deleted. Different types of mail (such as those with attachments or unread mail) may stay in your inbox for longer or shorter periods of time.
• While you can send mail to character in a different mode (Hardcore, Elite, and Hardcore Elite) you cannot attach items or Palladium in a cross-mode email. This follows the same rules as trading items.
• You canÂ’t mail quest items or non-tradable items (such as Dye Kits or a Skill Retrainer).

Via Hellgate London