Email Bounce back is sending the mail to the admin server mailbox

I am sending the mail using custom sender from xxx@gmail.com to yyy@gmail.com. Also i have set some auto reply in yyy@gmail.com (I will be out of office from ....).

But here the reply is being sent to the admin@dev.appiancloud.com instead of yyy@gmail.com.Can anyone suggest workaround to achieve this ?

Thanks,

Dinesh