主题是其中一个邮件标题 ，而不是标签。标题没有颜色，它们只是标题。您可以使用内容类型text / html为消息正文或消息部分之一应用颜色或任何其他

格式化属性，并在内容中添加适当的HTML标记。 br />


（如果某些邮件软件根据某些标准显示某些颜色的标题信息，这就是这个特定查看器的问题。这并不意味着标题信息包含颜色:-)。）

-SA

"Subject" is one of the mail headers, not "tag". Headers don't have colors, they are just headers. You can apply color or any other
formatting properties for the message body or one of message parts using content type "text/html", with appropriate HTML markup in content.

(If some mail software show some header information in some colors based on some criteria, this is the problem of this particular viewer. It does not mean that header information includes color :-).)

—SA