Contact Form 7 is the most popular contact form plugin in WordPress with above 5 million active installs. You can easily integrate it to many other popular platforms using the Advanced Form Integration plugin. It is supported in the basic free version of the AFI plugin.
When a user fills a form in your website, it can be connected as:
Please check out this video how easily an integration can be done.
Here is the list of supported form fields in Contact Form 7 that can be sent over to other platforms.