Tried forgot password on my wordpress admin site then the error appear
your host may have disabled the mail() function
The solution is
sudo apt-get install sendmail
sudo sendmailconfig
Just use the default configuration
sudo reboot
If still doesn’t work
find your hostname
hostname
nano /etc/hosts
127.0.0.1 localhost.localdomain localhost yourhostname
change yourhostname to exact hostname that appear when you type hostname