A message or messages are not being delivered by Messaging Gateway and the sender is receiving a bounce message indicating that the message was rejected due to it's size.
Reviewing the message audit logs for the message in Status > Message Audit Logs shows the following:
Details: 552 5.3.4 Message size exceeds fixed maximum message size
The destination mail server is configured to reject email messages that are above a certain size and SMG has attempted to deliver a message which exceeds that size.
This message is usually seen when communicating with Microsoft Exchange servers.
This is not an issue with Messaging Gateway. The destination mail server will need to be reconfigured to allow larger messages if Messaging Gateway is to deliver the queued messages to the downstream mail server.
If the destination mail server is Microsoft Exchange, please see the following Microsoft TechNet links for more information:
If another mail server is being used, please refer to your mail server's documentation.
You can confirm the upper limit on message size via telnet to the destination mail server. The 250-SIZE entry following the EHLO command will give the maximum allowed message size in bytes:
telnet mx.example.com 25
Connected to 192.0.2.25.
Escape character is '^]'.
220 mx.example.com ESMTP
250-mx.example.com says EHLO to 192.0.2.45:50218
221 2.3.0 mx.example.com closing connection
Connection closed by foreign host.