解决方法
使用POP3时,无法区分读取或未读取.它只能获取和删除消息.如果客户端获取新消息,则客户端(其自身记忆)尚未获取的所有消息都被客户视为新消息.服务器不关心消息的状态.它只是给你所有的消息.
从Wikipedia开始：
POP supports simple download-and-delete requirements for access to remote mailBoxes (termed maildrop in the POP RFC’s).[3] Although most POP clients have an option to leave mail on server after download,e-mail clients using POP generally connect,retrieve all messages,store them on the user’s PC as new messages,delete them from the server,and then disconnect. Other protocols,notably IMAP,(Internet Message Access Protocol) provide more complete and complex remote access to typical mailBox operations.