If you have trouble getting the PHP’s mail() function to work on your server.
If the function returned true, but never send the emails to target account.
Some ISP’s block port 25 (mail port), so you can’t send directly but you can send indirectly using your ISP’s mail server. 😉
Many email providers keep lists of IP addresses and block incoming mail, or move it immediately to a junk/spam folder.
There are some Open Source solutions to filter your mail problems..
You can check Open Source MTA here http://en.wikipedia.org/wiki/Comparison_of_mail_servers
Above MTA don’t handle integrated reporting, bounce management, and spam management, reporting.
PowerMTA: PowerMTA (this is not open source) provides the unique features and capabilities required by email service providers and enterprises to maximize the effectiveness of email marketing and customer communications, handle integrated reporting, bounce management, and spam management, reporting etc.