Have you ever been creating Canada Post labels and get this error when you click Create Label?
If you have gotten the error Rejected by SLM Monitor, this is due to Canada Post's servers throttling your Create Label request. Typically, Canada Post allows 20 requests per minute. If you receive this error frequently, you can request a limit increase on your Canada Post account.
In the event of a Canada Post server maintenance/outage, this error will transmit. Nonetheless, if you receive this error, give it a couple of minutes and try again.