Overview
The ‘421 Connection Timeout’ issue often occurs on sites attempting to send emails through an SMTP server. This indicates that the connection to the SMTP server has been timed out due to network issues.
Causes
This error typically occurs when:
- There are network connectivity problems between your server and the SMTP server
- The SMTP server is experiencing high traffic or temporary downtime
- Firewall or security settings are blocking the connection
- DNS resolution issues are preventing proper connection to the SMTP server
Solution
Since this is a temporal network issue, we suggest waiting and retrying after a while. However, if it doesn’t fix the error, consider trying the following:
- Checking your internet connection and network stability
- Verifying that the SMTP server is operational and not experiencing any known issues
- Reviewing your server’s firewall settings to ensure they’re not blocking SMTP traffic
- Confirming that DNS settings are correctly configured for the SMTP server
That’s it! Now you know how to troubleshoot and fix the ‘421 Connection Timeout’ error.
Want to explore other mailers WP Mail SMTP provides to improve email deliverability and avoid connection issues? Be sure to check out our complete guide to WP Mail SMTP mailers.