The invention relates to the technical field of data processing, and discloses a mail processing method, comprising the following steps: if a mail client receives a target mail, acquiring a receivingtime of the target mail; detecting whether there is a display operation on the target mail; if there is a display operation on the target mail, obtaining the display operation time, and determining whether there are related mails associated with the mail content in the mail client according to the mail content of the target mail; if there are related mails associated with the mail content in the mail client, combining and displaying the content of the related mails and the content of the target mail; if a reply sending operation to the target mail is detected obtaining the reply sending time of the target mail; and calculating the processing time of the target mail according to the receiving time, the display operation time, and the reply sending time. The invention also provides a mail processing device and a computer readable storage medium. The invention can improve the processing efficiency of mails and quantify the situation that the user processes the mails.