I'm trying to fix my problem regarding the plugin contact form 7. Basically the objective of my contact form is once the user submitted their application form with resume the contact form will send an email to the sender that their message has been received.

The problem is it works on a gmail address but not on yahoo address.

Here is the website that i am developing at the moment


I tried creating my own custom form and it works for yahoo email address. Has anyone tried fixing this problem.