Lookup for "552 2.4.3"
This status code indicates a successful delivery or other operation. Any details are simply notes.
Basic Status Code Details (552)
Requested mail action aborted: exceeded storage allocation
Enhanced Status Code Details (2.4.3)
Directory server failure
The network system was unable to forward the message, because a directory server was unavailable. This is useful only as a persistent transient error. The inability to connect to an Internet DNS server is one example of the directory server failure error.