Sendmail are enabled in our web hosting by default. To use it, please add this line to your .htaccess file (yes, no space after -f):
php_value mail.force_extra_parameters -fREPLACEYOUREMAILHERE
A word to share, you might want to consider using SMTP method than built in Mail() function. SMTP method is more reliable and it was implemented for serious email delivery and can reduce email missing problem. See this review.