Answer
A message was sent to an account on GMS but it was too large so GMS has sent a DSN error message back (as defined by Internet Standard RFC1891) to the sender of the message as well as rejecting the message at the protocol stage.
In this case, session Undefined was processing a message from a server at Undefined. The message was apparently from Undefined to Undefined and was rejected with
Undefined
This is the correct result, no action is required by you.
The maximum inbound message size is stored in "MaxMessageSize".
See Also:
Keywords:DSN too large RFC1891 8284