Adding troubleshooting & tips information of sending mail

[atachibana]

Please Refer below ticket for the base discussion.
https://core.trac.wordpress.org/ticket/53048

We should add

• The reason of why sending mail from WordPress system failure occurs.
• Workaround by specifying real address using wp_mail_from hook
• General notice such as "Please contact the admin or hosting company because there are various reasons etc."

[contactpp]

There maybe issue for simple mail function, smtp option is better for sending emails.