Email Quota Full?

My business associates are receiving this message when they send me an email. I have looked at my roundcube email and it is at 0% used. Is there something else I need to do? My emails are getting forwarded to a gmail account.

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:

 
   
    host bospopproxy16.eigbox.net [10.20.20.16]
    LMTP error after BDAT 82342 LAST: 552 5.2.2  Quota exceeded (mailbox for user is full)