MimeMessage类位于javax.mail.internet包下，是用于发送邮件的一个类，其中header变量包含了众多与邮件头信息有关的变量
| 索引序号 | 变量名 | 含义 |
|---|---|---|
| 0 | Return-Path | |
| 1 | Received | |
| 2 | Resent-Date | |
| 3 | Resent-From | |
| 4 | Resent-Sender | |
| 5 | Resent-To | |
| 6 | Resent-Cc | |
| 7 | Resent-Bcc | |
| 8 | Resent-Message-Id | |
| 9 | Date | 发送时间 |
| 10 | From | 发件人 |
| 11 | Sender | |
| 12 | Reply-To | |
| 13 | To | 收件人 |
| 14 | Cc | 抄送人 |
| 15 |
Bcc |
密送人 |
| 16 | Message-Id | |
| 17 | In-Reply-To | |
| 18 | References | |
| 19 | Subject | 邮件主题 |
| 20 | Comments | |
| 21 | Keywords | |
| 22 | Errors-To | |
| 23 | MIME-Version | |
| 24 | Content-Type | |
| 25 | Content-Transfer-Encoding | |
| 26 | Content-MD5 | |
| 27 | ： | |
| 28 | Content-Length | |
| 29 | Status |
a