ellite/Wallos · critical · Exception

$this->lang('execute') . $this->Sendmail

Error message

$this->lang('execute') . $this->Sendmail

What it means

sendmailSend() (Sendmail transport, called from postSend) throws the localized 'execute' text plus $this->Sendmail with STOP_CRITICAL when @popen($sendmail, 'w') fails while $SingleTo is enabled — i.e., PHP could not start the sendmail binary process to write the message to.

Solutions

  1. Verify the sendmail binary exists and is executable at $mail->Sendmail (default /usr/sbin/sendmail -t -i); adjust $mail->Sendmail accordingly
  2. Install a sendmail-compatible MTA (postfix, msmtp) in the environment, or switch to SMTP: $mail->isSMTP() with host/auth settings
  3. Check open_basedir/safe_mode and OS-level restrictions that block popen
  4. Log the Sendmail path and test it manually: echo test | /usr/sbin/sendmail -t -i

Example fix

// before
$mail->isSendmail();
$mail->Sendmail = '/usr/sbin/sendmail'; // binary missing
// after
if (!is_executable('/usr/sbin/sendmail')) {
    $mail->isSMTP();
    $mail->Host = 'smtp.example.com';
    $mail->SMTPAuth = true;
    $mail->Username = '...';
    $mail->Password = '...';
} else {
    $mail->isSendmail();
}
Defensive patterns

Strategy: try-catch

Validate before calling

$cmd = explode(' ', $mail->Sendmail)[0]; if (!is_executable($cmd)) { throw new RuntimeException("Sendmail binary not executable: $cmd"); }

Try / catch

try { $mail->send(); } catch (PHPMailer\PHPMailer\Exception $e) { if (str_contains($e->getMessage(), 'execute')) { log_mta_failure($e->getMessage()); fallback_to_smtp($mail); } else { throw $e; } }

Prevention

When it happens

Trigger: $mail->isSendmail() with $mail->SingleTo=true; popen fails because the Sendmail path ($mail->Sendmail, default /usr/sbin/sendmail) does not exist or is not executable, safe_mode/open_basedir restrictions, or process/fork limits.

Common situations: Local dev machines without a sendmail-compatible MTA installed, misconfigured Sendmail path (e.g., pointing to msmtp that is not installed), containers stripped of sendmail, PHP deployed without permission to execute binaries.

Related errors

AI-assisted analysis of ellite/Wallos@52820e87ca (2026-09-13). Data as JSON: /api/errors/097489b188fb43dd. Report an issue: GitHub.

Appendix: source

Thrown at libs/PHPMailer/PHPMailer.php:1767

            //allow sendmail to choose a default envelope sender. It may
            //seem preferable to force it to use the From header as with
            //SMTP, but that introduces new problems (see
            //<https://github.com/PHPMailer/PHPMailer/issues/2298>), and
            //it has historically worked this way.
            $sendmailFmt = '%s -oi -t';
        }

        $sendmail = sprintf($sendmailFmt, escapeshellcmd($this->Sendmail), $this->Sender);
        $this->edebug('Sendmail path: ' . $this->Sendmail);
        $this->edebug('Sendmail command: ' . $sendmail);
        $this->edebug('Envelope sender: ' . $this->Sender);
        $this->edebug("Headers: {$header}");

        if ($this->SingleTo) {
            foreach ($this->SingleToArray as $toAddr) {
                $mail = @popen($sendmail, 'w');
                if (!$mail) {
                    throw new Exception($this->lang('execute') . $this->Sendmail, self::STOP_CRITICAL);
                }
                $this->edebug("To: {$toAddr}");
                fwrite($mail, 'To: ' . $toAddr . "\n");
                fwrite($mail, $header);
                fwrite($mail, $body);
                $result = pclose($mail);
                $addrinfo = static::parseAddresses($toAddr, true, $this->CharSet);
                $this->doCallback(
                    ($result === 0),
                    [[$addrinfo['address'], $addrinfo['name']]],
                    $this->cc,
                    $this->bcc,
                    $this->Subject,
                    $body,
                    $this->From,
                    []
                );
                $this->edebug("Result: " . ($result === 0 ? 'true' : 'false'));

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