Mail service method for searching for mail in a mail service system. At least one of a plurality of items configuring a format of mail data is set as at least one card item. A keyword is received, and for mail data that includes the keyword is searched for. A separate mail list for the at least one card item is configured by selecting mail data including the keyword in the at least one card item, and creating a mail card including a tag indicating the at least one card item and a link to the configured separate mail list. A search result that including the created mail card is provided.