邮件格式规范问题（严格遵守规范的目标邮箱服务器会拒绝） #1111
Description
host gmail-smtp-in.l.google.com[xx.xx.xx.xx] said: 550-5.7.1 [xx.xx.xx.xx] Messages missing a valid Message-ID header are not accepted. For more information, go to https://support.google.com/mail/?p=RfcMessageNonCompliant and review RFC 5322 specifications. 41be03b00d2f7-bc376795547si8867543a12.723 - gsmtp (in reply to end of DATA command)
因为缺少必需的Message-ID头字段，这是RFC 5322标准的硬性要求。
在发送邮件时没有自动生成或显式添加Message-ID头
Gmail严格执行RFC 5322标准，将此视为垃圾邮件或配置不当的迹象