$storeScope = MagentoStoreModelScopeInterface::SCOPE_STORE;
        $transport = $this->_transportBuilder->setTemplateIdentifier(1)
                ->setTemplateOptions(['area' => MagentoBackendAppAreaFrontNameResolver::AREA_CODE, 'store' => 1])
                ->setTemplateVars(['data' => $postObject])
                ->setFrom('XXXX@gmail.com', $storeScope)
                ->addTo('XXXX@gmail.com', $storeScope)
                ->setReplyTo('XXXX@gmail.com')
                ->getTransport();
        echo $transport->sendMessage();

public function setFrom($from)
    {
        $result = $this->_senderResolver->resolve($from);
        $this->message->setFrom($result['email'], $result['name']);
        return $this;
    }

->setFrom($this->scopeConfig->getValue(self::XML_PATH_EMAIL_SENDER, $storeScope))