问题描述
发送电子邮件时，通过RCTP TO：命令在SMTP对话期间给出收件人列表。之后，在DATA命令中，指示To，Cc，bcc等标题字段。 RCPT TO收件人列表是否必须与DATA命令中指示的标题相匹配？
When sending an email, the recipient list is given during the SMTP dialogue through RCTP TO: command. Later, in DATA command, header fields like 'To', 'Cc','bcc' are indicated. Does this RCPT TO list of recipients have to match with the headers indicated in DATA command?
此外，如果收件人未在RCPT TO中显示，而在收件人字段中的电子邮件标题，是否会传递给不在RCPT TO的收件人？
Also, if the recipient is not indicated in RCPT TO, but in the To field of email header, is it going to be delivered to the recipient not in RCPT TO ?
推荐答案
不，他们没有匹配。当邮件发送时，SMTP服务器（也称为邮件传输代理或MTA）正在创建一个所谓的SMTP信封，其中包含邮件的收件人和发件人（请参阅）：
No, they don't have to match. When the message is sent, the SMTP Server (aka Message Transfer Agent or MTA) is creating a so called SMTP envelope which contains the recipients and the sender of the message (see RFC5321):
实际上，RCPT TO：Command有更多收件人的消息头，通常情况下是使用盲拷贝bcc：（请参阅）：
It is, actually, quite often that the RCPT TO: Command has more recipients that the header of the message - one common case is the usage of "blind copies" bcc: (see RFC5321):
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