I tried enabling this option
Send Email Using '-f' Option
Enable this option only if you are on a Unix/Linux server and mails are not being sent.
and I get this error message in my box
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:
mminnis@hotmail.com
unrouteable mail domain "hotmail.com"
