There is a feature called BoxTrapper Spam Trap in cPanel. If you have enabled this option for your domain then whenever anyone sends email they will need to reply the automated mail generated by BoxTrapper Spam Trapper and then you will receive the email to your account. However, it is advisable not to enable this option. You can disable this option server wide by following the below steps:
[1] Login to your WHM.
[2] Go to Tweak Settings.
[3] Uncheck BoxTrapper Spam Trap option and save it.
Regards,
Kevin