SmtpMailer – 503 5.5.2 Send hello first FIX

<?php
...

protected function connect(): void
	{
		$this->connection = @stream_socket_client(// @ is escalated to exception
			($this->secure === 'ssl' ? 'ssl://' : '') . $this->host . ':' . $this->port,
			$errno, $error, $this->timeout, STREAM_CLIENT_CONNECT, $this->context
		);
		if (!$this->connection) {
			throw new SmtpException($error ?: error_get_last()['message'], $errno);
		}
		stream_set_timeout($this->connection, $this->timeout, 0);
		$this->read(); // greeting

                $this->write("HELO $this->clientHost", 250);
		if ($this->secure === 'tls') {
			$this->write('STARTTLS', 220);
			if (!stream_socket_enable_crypto(
				$this->connection,
				true,
				STREAM_CRYPTO_METHOD_TLS_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT | STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT
			)) {
				throw new SmtpException('Unable to connect via TLS.');
			}
			$this->write("EHLO $this->clientHost", 250);
		}

		$this->write("EHLO $this->clientHost");
		$ehloResponse = $this->read();
		if ((int) $ehloResponse !== 250) {
			$this->write("HELO $this->clientHost", 250);
		}

		if ($this->username != null && $this->password != null) {
			$authMechanisms = [];
			if (preg_match('~^250[ -]AUTH (.*)$~im', $ehloResponse, $matches)) {
				$authMechanisms = explode(' ', trim($matches[1]));
			}

			if (in_array('PLAIN', $authMechanisms, true)) {
				$credentials = $this->username . "\0" . $this->username . "\0" . $this->password;
				$this->write('AUTH PLAIN ' . base64_encode($credentials), 235, 'PLAIN credentials');
			} else {
				$this->write('AUTH LOGIN', 334);
				$this->write(base64_encode($this->username), 334, 'username');
				$this->write(base64_encode($this->password), 235, 'password');
			}
		}
	}

...
?>