What does a 'timeout after end of message' error from blocklist.de mean and how do I fix it?
Summary
What email marketers say8Marketer opinions
Email marketer from StackOverflow suggests checking your mail server configuration to ensure that the connection timeout settings are appropriately configured. A short timeout value might cause premature connection closures. Also, verify that your server has enough resources to handle the number of outgoing connections.
Email marketer from Reddit recommends examining your mail server logs to pinpoint the exact moment the timeout occurs. This can help identify whether the issue is happening before, during, or after message transmission. Look for any related error messages or warnings in the logs.
Email marketer from MXToolbox indicates that some firewalls or security software can interfere with SMTP connections, causing timeouts. Ensure that your firewall allows outgoing SMTP traffic on port 25, 587, or 465, and that no security software is blocking or throttling connections.
Email marketer from Litmus shares the recommendation to use a reputable SMTP service that adheres to all best practices. They often have better delivery rates and may avoid these type of errors.
Email marketer from AuthSMTP says that some anti-virus software or other internet security software can cause issues with SMTP. Ensure you test sending from a variety of computers with different setups.
Email marketer from Mailjet suggests checking the resource utilization of your mail server, including CPU, memory, and disk I/O. Insufficient resources can cause the server to become unresponsive, leading to timeouts. Consider upgrading your server hardware or optimizing your server configuration.
Email marketer from Email on Acid shares that network congestion or intermittent network connectivity issues between your mail server and the recipient's server can lead to timeouts. Consider using a more reliable internet connection or a dedicated mail relay service to improve stability.
Email marketer from SuperUser mentions that some recipient mail servers have aggressive anti-spam measures that can cause timeouts if your email is flagged as suspicious. Ensure that your email content is not triggering spam filters and that your sending reputation is good.
What the experts say4Expert opinions
Expert from Word to the Wise explains that timeout errors can sometimes indicate a compromised SMTP server attempting unauthorized activities. These could be attempts to relay spam through your infrastructure. Securing your server, reviewing your outgoing mail queue for unusual activity, and ensuring strict authentication are critical steps. It's a common issue when an attacker has gained access and is exploiting the server for illicit purposes, leading to erratic behavior like premature connection termination.
Expert from Email Geeks explains that the 'timeout after end of message' error from blocklist.de indicates a violation of the SMTP specification and may not directly relate to spam blocking. Laura suggests checking if the IP is listed and how long connections are kept open after DATA. Additionally, they emphasize the importance of sending a QUIT command before closing the connection.
Expert from Email Geeks explains that the 'harvesting' report type from blocklist.de indicates the IP address is exhibiting behavior that looks like an attack on the SMTP server to discover active addresses, also known as address harvesting or dictionary attacks. This is not related to incorrect protocol closure, but more to do with sending to invalid email addresses.
Expert from Spamresource.com explains that 'Timeout after End-of-Message' often arises from non-compliance with SMTP protocols. Servers should properly send the QUIT command and await acknowledgment rather than abruptly closing connections. Incomplete or improperly terminated SMTP sessions often trigger this error, reflecting poor coding practices in mail handling software. The recommendation is to check if you are properly implementing the protocol
What the documentation says4Technical articles
Documentation from blocklist.de explains that 'Timeout after End-of-Message' indicates that the remote server closed the connection prematurely after the message content was sent, violating SMTP standards. This is often caused by server misconfiguration or network issues on the sender's side.
Documentation from RFC 5321 (the SMTP standard) specifies that a conforming SMTP server MUST NOT close the transmission channel except as noted in the RFC. Premature closing after the DATA command constitutes a protocol violation and can result in the 'timeout after end of message' error. Ensure your server adheres to the complete SMTP transaction sequence.
Documentation from SendGrid suggests using network monitoring tools to check the latency and packet loss between your server and the recipient's server. High latency or packet loss can contribute to timeouts. Also, ensure that your DNS records are correctly configured and that your IP address is not blacklisted.
Documentation from Postfix.org emphasizes that strict adherence to SMTP protocol standards is crucial for reliable email delivery. Ensure your mail server correctly implements the QUIT command and waits for the remote server to close the connection gracefully. Closing the connection prematurely can lead to timeout errors.