WordPress Contact Form Mail via SMTP 

Default WordPress settings use phpMail, an older out-of-date process that generally results in your form mail being rejected by the sending and/or receiving server. Major ISPs dictate what email they will allow through to their users. To resolve the issue, you can authenticate all your form mail(and your WordPress notification emails) with SMTP.

There are many plugins out there in the WordPress plugin repository to accomplish SMTP mail. Of this list, 2 plugins are seen more often than any of the others, Easy WP SMTP and WP Mail SMTP. Both plugins require the same information to complete the setup, the information from your email client. 

You will need a real email address, its password, and your email client settings to successfully configure the plugin. When entering your email settings(SMTP) into either plugin you will want to use the hostname of your mail server, not mail.yourdomain.com. For instance:

Use:
rs1.hostrocket.com

Not:

mail.example.com

Your SMTP port will either be 465(STARTTLS) or 587(No Encryption).

If you are going to use Gmail or Yahoo or other 3rd party email service you will need to select the proper SMTP mailer. If you are using email hosted here, you will select `Other SMTP` as your preferred mailer.

Make use of the `Send Test Email` feature as it will let you know if there are any issues in your configuration.