akrambhatti on "Contact us from 7 sending error"

I am using contact form 7 Version 4.1.2 | By Takayuki Miyoshi on my different website, from last few days i am seeing error and no email sending,
Failed to send your message. Please try later or contact the administrator by another method.

this error is showing, it is not possible for me, to instal antother plugin, i have updated this plugin but still no change, please anyone know how i can do this?