Query: When users try to register with your blog or change their passwords by entering their username and email, WordPress indicates that their password has been emailed to them, but it is never received.
Solution 1: WordPress uses the standard PHPMail() function, which uses sendmail. No account information is needed. But some hosting provider is blocking PHPMail() function from the server due spamming problem. Hence, one need to use SMTP authenticated script into his code.
Solution 2: One can use plugins to send email like wpPHPMailer.