Cookie Issue – Nginx Cache

Hello,

I use this contact form plugin as it is one of the only that I have found that works fine in a website that uses an ajax theme.

I am trying to use nginx caching, but it is not working due to a cookie set by your plugin:

cntctfrm_send_mail=deleted; expires=Thu, 01-Jan-1970 00:00:01 GMT; Max-Age=0

Could you tell me how I can remove this please?

Thank you.