Hello @kstyuen,
In reality there are many possible causes, please, check the following settings:
1. Go to the settings page of the plugin, through the menu option: “Settings/Calculated Fields Form”. Untick the checkbox: “Modify the eMails Headers”, and press the “Update” button.
2. Press the “Settings” button corresponding to your form.
3. Select the “From fixed email address indicated below – Recommended option” option for the attribute: “Send email From”
4. Enter an email address belonging to your website’s domain in the attribute: “From email (for fixed “from” addresses)”
Note: The email services compare the address in the email header, with the domain that send it, and if they don’t match, the email can be classified as spam, or even worst, as a phishing email.
5. Enter the email address where receive the notification email, through the attribute: “Destination emails (comma separated)”
If you want sent a confirmation email to the users.
6. Insert an email control in the form.
7. Select the “Yes” option for the attribute: “Send confirmation/thank you message to user?”
8. Select the email control in the list: “Email field on the form”.
Pay attention: The list “Email field on the form” allows multiple selection, so, the field should be selected explicitly, it is not sufficient that the email field appears in the list. If you want send a confirmation email to the users you must click over the corresponding field in the list.
If your form is associated to PayPal and the option: “When paid: AFTER receiving the PayPal payment” was selected in the attribute: “When should be sent the notification-confirmation emails?”, the plugin won’t send the notification emails until receive a payment confirmation from PayPal, please, be sure the IPN is enabled in your PayPal account.
Finally, if the issue persists, I recommend you to use a SMTP server for sending the emails instead the web server. Ask to your hosting provider the hostname and access to the SMTP server (all hosting providers include one), and install in your WordPress any of the SMTP connection plugins distributed for free in the WordPress directory.
Best regards.
