Mail is the private messaging system of the game. The mail system allows users to send gear, gold, and private messages to one player. Sending mail costs ten gold. It is only possible to attach one gear item per message.
To use the mail system, open the GearQuest profile page of the player and click on the 'Send Private Mail' option. If you wish to mail gear, open the backpack and in the item menu choose 'Mail Item' option (only items that are not soulbound will have this option). At the bottom, you can choose to request the player to pay for the item you are sending.