● 软退件：电子信箱暂时无效，虽然信件可能会无法寄出，但只是暂时性的。也就是说，这类型的电子信箱依然有效，不应该从名单中移除。那么，有哪些原因可能导致信箱暂时无效？可能是因为收件人的信箱太满，直到清理收件匣以前都无法再收信。也有可能是因为您在工作时间以外的时间点寄信，暂时收到了自动回复。又或者，单纯是因为系统暂时故障而已。软退件的电子信箱只是暂时无法收信，一旦问题解决后，依然是可以收信的名单。

● soft return: e-mail is temporarily invalid. Although letters may not be sent, they are only temporary. In other words, this type of e-mail is still valid and should not be removed from the list. So, what are the reasons that may cause the mailbox to be temporarily invalid? It may be that the recipient's mailbox is too full to receive letters until the inbox is cleaned. It may also be that you have received an automatic reply temporarily when you send a letter outside working hours. Or simply because the system is temporarily out of order. The e-mail of soft returned items is only temporarily unavailable. Once the problem is solved, it is still a list of acceptable items.

而清理名单的作用，正是为了要提升企业与订阅用户之间的互动，因为您的寄送对象是确实存在的邮件地址，而且收件人实际上会开启信件或点击链接。同理，如果您移除久未开信的无效信箱，便能增加与其他收件人的互动。不只如此，您可以选择较小的的营销方案，将预算集中运用在会开信的订阅用户，这样一来，您也更有可能成功传递您的讯息。