我在 mail-tester.com 上得到 6.1/10 的分数，其中 DMARC 验证是唯一相关的惩罚 (-3)。
* Your DKIM signature is valid
* Your message failed the DMARC verification
A DMARC policy allows a sender to indicate that their emails are protected by SPF and/or DKIM, and give instruction if neither of those authentication methods passes. Please be sure you have a DKIM and SPF set before using DMARC.
You are not allowed to send a message with this address
DMARC DNS entry found for the domain _dmarc.mail.example.com: …