A method for customizing a mail history including generating a mail tree composed of all received mails belonging to a same topic; receiving a user input indicating a mail to be replied to and a mail to be referred to which are selected by the user, the mail to be replied to and the mail to be referred to being located on different branches of the mail tree; acquiring a first plurality of mails on a first path from a root mail of the mail tree to a child mail of the mail to be replied to, and a second plurality of mails on a second path from the root mail to a child mail of the mail to be referred to; and merging the first plurality of mails and the second plurality of mails to generate a merging result as the mail history.