The receiving mail server is not responding to connection attempts. The server may be down, unreachable due to network issues, or a firewall may be blocking the connection. Your MTA will retry automatically.
What Does Error 4.4.1 Mean?
Enhanced status code 4.4.1 means your sending server could not establish a connection with the recipient mail server. The server did not respond to the TCP connection attempt on port 25. This is typically a network-level or server availability issue.
Common causes include the recipient server being temporarily offline, DNS resolution issues where MX records point to an unreachable IP, or network routing problems between your server and the destination. This is usually a temporary condition.
Common Causes
- Recipient mail server is temporarily offline
- Network routing issue between sending and receiving servers
- MX records point to an unreachable IP address
- Firewall blocking inbound port 25 on the recipient server
- DNS resolution delay or failure for MX records
How to Fix Error 4.4.1
- Allow automatic retries - most resolve within hours
- Verify recipient domain MX records using MX Lookup
- Check if the issue is specific to one recipient domain or widespread
- Contact recipient postmaster if unresponsive for 24+ hours
Frequently Asked Questions
Bounce code 4.4.1 means the sending mail server attempted to connect to the recipient's server but received no response -- the connection timed out. This is a temporary error indicating the recipient's mail server is unreachable, possibly due to being offline, experiencing network issues, or being blocked by a firewall. Your sending server will automatically retry delivery over the next several days.
First, verify the recipient's email address and domain are correct. Check that your DNS is resolving the recipient's MX records properly. Ensure your firewall is not blocking outbound connections on SMTP port 25. If the problem affects all outgoing mail, check your server's network connectivity and DNS configuration. If it only affects one domain, the issue is likely on the recipient's end -- wait and retry, as the problem is often temporary.
Usually not. The 4.4.1 error most often indicates the recipient's server is unreachable or not responding. However, it can occasionally be caused by your own network issues, DNS misconfiguration, or firewall rules blocking outbound SMTP traffic. To determine the cause, try sending to a different domain -- if other domains work fine, the problem is on the recipient's side. If all outgoing mail fails, investigate your own server's network connectivity, DNS settings, and firewall rules for port 25 access.