Part1:
Step1 : Goto Sendmail Folder -> sendmail.ini
smtp_server=smtp.gmail.com
smtp_port=587 (or use 25 if it not working)
error_logfile=error.log
debug_logfile=debug.log
auth_username=****@gmail.com
auth_password=*******
force_sender=****@gmail.com
Step2 : PHP -> php.ini
[mail function]
sendmail_path = "\"C:\xampp\sendmail\sendmail.exe\" -t"