下载图像后，会向垃圾电子邮件的发件人发送Web信号通知，告知收件人的电子邮件地址是有效的。

After the images are downloaded, a Web beacon notification is sent to the sender of the junk email that informs the sender that the recipient email address is valid.

youdao

下载图像后，会向垃圾电子邮件的发件人发送Web信号通知，告知收件人的电子邮件地址是有效的。

After the images are downloaded, a Web beacon notification is sent to the sender of the junk email that informs the sender that the recipient email address is valid.

youdao