log has root or use sudo apt-get install php-pear
pear install mail
pear install Net_SMTP
pear install Auth_SASL
pear install mail_mime
apt-get install postfix
vi /etc/php5/apache2/php.ini (set sendmail path to /usr/sbin/sendmail -t -i)
Reboot apache gracefully apachectl graceful
Thanks to info, original answer at https://www.digitalocean.com/community/questions/php-mail-function-enable