FAQ / Server Products

I get the error 421 4.4.2 Message submission rate for this client has exceeded the configured limit when sending email to my Exchange server. What could be wrong?
On your Exchange Hub Transport server, run the powershell:
Get-ReceiveConnector | fl name,messageratelimit

This will show you the maximum rate that a client can send messages through that specific connector.
Use the Set-ReceiveConnector cmdlet to change this value for the specific Receive Connector.
Unless you create a custom connector and scope it only to the specific users IP address, I do not think you can configure this on a per-user basis.

Also note, if you have multiple Hub Transport servers, you will need to set this on each server for the designated connector.

Raising the limits may be more complex than just providing a single
value in a set-receiveconnector cmdlet.

-MaxInboundConnection
-MaxInboundConnectionPercentagePerSource
-MaxInboundConnectionPerSource
-MaxRecipientsPerMessage
-MessageRateLimit
-MessageRateSource

Assuming youre NOT using an Edge server, the -MessageRateSource is
already unlimited. That means youre hitting one of the other
limits, probably the -MaxInboundConnectionPercentagePerSource (default
2%) or -MaxInboundConnectionPerSource (default of 100).

If your -MaxInboundConnection is 5000, then 2% of that would be 100 if
there were no other connections in use. If there were 100 connections
in use then it would be 4900*0.02 or 98.

There are also the following guides: