Error Description

SMTP error 420 is a transient or "4xx" error code returned by a mail server to indicate that it has encountered a temporary issue that is causing a delay in processing the email message. Unlike permanent errors (5xx codes), SMTP error 420 suggests that the server is experiencing a temporary problem, and the email delivery may succeed if the sender retries at a later time.

What's Causing This Error?

SMTP error 420 can be caused by various temporary issues, including::

• Server congestion: The mail server is currently handling a high volume of incoming email traffic, leading to delays in processing new messages.
• Greylisting: Some mail servers use greylisting as a spam-fighting technique. When an unknown sender attempts to send an email, the receiving server may initially reject it with a 420 error. If it's a legitimate sender, the sending server will retry the delivery after a delay, and the email will be accepted.
• ‍Temporary server issues: Server hardware or software issues, network problems, or other transient issues can lead to SMTP error 420.

‍

How to fix SMTP Error 420?

• Wait and retry: In most cases, SMTP error 420 is a temporary issue caused by server congestion or other transient problems. The best approach is to wait and retry sending the email later. The receiving server should eventually be able to accept the message.
• ‍Check for greylisting: If you suspect greylisting is causing the error, simply waiting and retrying the email should resolve the issue when the receiving server accepts the email upon the retry.
• ‍Investigate server issues: If you consistently encounter SMTP error 420 when sending emails to a specific recipient, it's possible that the recipient's mail server is experiencing server issues. You may want to contact the recipient's email administrator for assistance.

SMTP Error 420 Examples

Example 1: "420 Temporary failure, please try again later."

Example 2: "420 Greylisted - Try again in 15 minutes."

Example 3: "420 Service temporarily unavailable due to server maintenance. Please retry later."