What Is Causing This Error?
The error 421-4.7.0 issue usually occurs on sites sending emails through an SMTP server. It indicates that the TLS configuration required by the email recipient(s) is missing or not properly configured on your SMTP server.
This can often occur due to outdated TLS (Transport Layer Security) version, incorrect SMTP configuration, or lack of TLS support.
Resolving the Error – Solution
To fix this error, check your SMTP server settings to ensure it’s properly configured. Check that TLS is enabled for your SMTP server and that you’re using the latest version of TLS.
Note: If you’re unsure where to locate the TLS settings for your SMTP server, be sure to contact them for guidance.
We also suggest reviewing the TLS protocol configuration to ensure you’re not using the wrong port. The recommended port for TLS protocol is 587.
That’s it! Now you know how to fix Error 421-4.7.0: TLS required for RCPT domain issue.
If you’d like to learn how to troubleshoot other common errors, check out the following tutorials: