sendmail_path in php.ini for unix [full name of email sender]
Try the version below:
sendmail_path = /usr/sbin/sendmail -t -i -F"Full Name" -f'emailaddress@example.com'WARNING
It will work with "real sendmail" (sendmail provided by sendmail.org).
It may not work with some "sendmail look alike" provided by other MTAs e.g. postfix, exim, ...