Docs Error Library Connection Errors Error 421: Service Not Available, Closing Transmission Channel

Error 421: Service Not Available, Closing Transmission Channel

What Is Causing This Error?

‘Error 421: Service not available, closing transmission channel’ is a temporary error indicating that the email server cannot accept more connections or handle additional email requests at the given time.

This error can occur due to server overload, maintenance, or set limits on simultaneous connections.

While the cause of the error may vary, it typically means there’s a temporary issue with the recipient’s server or email account.

Resolving the Error – Solution

The initial step to fix this error is typically to wait and retry sending the email at a later time since the issue is often temporary.

If the error arises after resending the email at a later time, it’s advisable to ensure that your email client or application is not flooding the server with multiple simultaneous connections. If the error persists, it might be beneficial to review the sending limits set by your email service provider.

Should continuous issues occur, contacting your email service provider’s support team can offer more specific guidance and potential solutions.

That’s it! Now you know the common causes of the 421 error and how to resolve it.

If you’d like to learn how to troubleshoot other common errors, check out the following tutorials: