You can receive and send mail by tapping Mail in the top right Menu list in game. 

■ Receive Mail

 - You can receive up to 50 personal and guild mail, after which you will not be able to receive any more. 

 - Received mail has a storage period and is deleted after the storage period expires. 

 - You can use the Lock feature in the Received Mail list to keep it forever. 

■ Send Mail

 - You can send personal and guild mail up to 20 times a day, and the number of sent mail is reset daily at 21:00(UTC).

 - Sending mail costs Gold, and the amount of Gold required increases with the number of mail sent.