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Incident report
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Resolution: Software failure
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Trivial
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None
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6.4.8
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None
Steps to reproduce:
- No changes in environment
- Send a test mail through the server (localhost:25, plain email)
- Server logs will show `failed to send email: error receiving answer on . request: [4] Interrupted system call`
Result:
The test email goes through just fine, but the interface shows an error.
For normal problem triggers, they are sent 3 times. I'm guessing because of a retry-mechanism built into the server. And then they still show as failed.
Even though I got 3 mails.
Expected:
No errors on sending.
Attached:
tcpdump from the server where I did the test via the interface (tcp.stream eq 0):
As you can see in packet 18, the "\r\n.\r\n" is sent. But then nothing.
When I run a simple php script mimicking the zabbix flow observed, I get the result in "tcp.stream eq 3":
<?php // SMTP server settings $smtpServer = "mail.salvania.be"; $smtpPort = 25; // Sender and recipient details $from = "[email protected]"; $to = "[email protected]"; // Email content $message = "From: \"Zabbix\" <[email protected]>\r\n". "To: <[email protected]>\r\n". "In-Reply-To: <0.e6aaeb1c51ec501da39a0f92f4e6e84e.1.72717f1bd11d285a2415c519590d68d2@zabbix.com>\r\n". "Date: Fri, 10 Nov 2023 09:23:23 +0100\r\n". "Subject: Test subject\r\n". "MIME-Version: 1.0\r\n". "Content-Type: text/plain; charset=\"UTF-8\"\r\n". "Content-Transfer-Encoding: base64\r\n". "\r\n". 'VGhpcyBpcyB0aGUgdGVzdCBtZXNzYWdlIGZyb20gWmFiYml4'; // Function to send command and receive response function sendCommand($smtpConnection, $command, $fetch = true) { foreach( explode("\n", rtrim($command)) as $line ) { $line = rtrim($line); echo "> {$line}\n"; } fputs($smtpConnection, $command); if ($fetch) echo "< " . fgets($smtpConnection); } // Open a TCP connection to the SMTP server $smtpConnection = fsockopen($smtpServer, $smtpPort, $errno, $errstr, 10); // Check if the connection is successful if (!$smtpConnection) { die("Failed to connect to the SMTP server: $errstr ($errno)"); } // Read the welcome message from the SMTP server echo "< " . fgets($smtpConnection); // Send the EHLO command and handle multi-line response sendCommand($smtpConnection, "HELO salvania.be\r\n"); // Send the MAIL FROM command sendCommand($smtpConnection, "MAIL FROM: <$from>\r\n"); // Send the RCPT TO command sendCommand($smtpConnection, "RCPT TO: <$to>\r\n"); // Send the DATA command sendCommand($smtpConnection, "DATA\r\n"); // Send the email headers and body sendCommand($smtpConnection, $message, false); sendCommand($smtpConnection, "\r\n.\r\n"); // Send the QUIT command sendCommand($smtpConnection, "QUIT\r\n"); // Close the connection fclose($smtpConnection); ?>
