Please help me

Why I am getting this error
Failed to send your message. Please try later or contact the administrator by another method.

after submitting the form…
https://www.qudusdesign.com/custom-designs/
https://www.qudusdesign.com/hhenok-mailing-list/

Please help me

At email section i have added this :

Mail
In the following fields, you can use these mail-tags:
[your-name][your-email][your-message][YourDesign]
To
[email protected]
From
[email protected]
Subject
Custom Designs
Additional Headers
Message Body

The page I need help with: [log in to see the link]