Yahoo: 451 Message temporarily deferred due to unresolvable RFC.5321 from domain-526互联

Hello,

Thank you for contacting Yahoo Postmaster.

The error you’re getting is caused by an issue with your From address.

These errors indicate that the domain used to the right of the @ in the MAIL FROM does not appear to be a real domain.
We determine if the domain name exists by using an SOA query; therefore, if multiple subdomains are used in MAIL FROM commands, then besides setting up a DNS A or MX record (perhaps using a wildcard), then SOA records must be set up as well.
This error can be returned as either a timeout/servfail (451) or a permfail (554)

You’ll need to work with your provider to make sure your From address meets these requirements to resolve the error.

Thanks for understanding.

Have a great day!

Warm regards,

Emilia

Yahoo Postmaster

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正常情况soa记录应该是dns自动配置的，可能有些不是主流dns服务商没做好导致soa缺失了，补上就好了