参照:http://help.163.com/09/1223/14/5R7P6CJ600753VB8.html
参照:https://support.office.com/zh-cn/article/%E7%94%A8%E4%BA%8E-outlook-%E7%9A%84-pop-%E5%92%8C-imap-%E7%94%B5%E5%AD%90%E9%82%AE%E4%BB%B6%E8%AE%BE%E7%BD%AE-8361e398-8af4-4e97-b147-6c6c4ac95353