sendmail_path "/bin/true" ? Really? If you know what that is, there's no way /bin/true can send an email.
What OS are you running? Does it have an SMTP program (MTA, "Mail Transport Agent") installed?
Write a script you can easily call that sends an email. Run it, pointing to an email address you can access & read, and see if you get mail.
Read the mail-server logs.
If you don't receive the mail, change your configuration. Or, better yet, find someone else who can assist you.