Email address not working and can let me get into legal issues because of this

The legal department send me an sms to email my proof of payment, when I email my proof of payment, they indicate it is urgent and that I will be handed over so I am not sure what to do. The email address comes back with the below, so how do I sort my payments out, it does not work properly & the email address I did add to the email is the same as per sms: "A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:"

(ultimately generated from ***) This email account's owner has suspended delivery for the account.