SMTP error 512 occurs when the recipient's email domain is not resolvable via a valid DNS record.
This error usually occurs when the user misspells the recipient's email domain, it is crucial to ensure that the email domain is correct. Additionally, the domain requires a valid DNS record. DNS Lookup can help check if the necessary MX records are available for the recipient's mail server to operate.
If nothing is wrong with the criteria mentioned above, the connectivity to resolving the DNS record from the sender's mail server requires verification.
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