I have this problem on my application to relay email through port 587 of our Exchange 2010: error prompt was 4.4.2 Message submission rate for this client has exceeded the configured limit.

I understand this is due to the MessageRateLimit of my receiver connector. I checked the limit is 5 and limit by user (MessageRateSource), and I think the problem probably will be fixed by increasing the limit to 50 or 100. However I would like to understand this configuration more (how if I set it to 50 now and it hit the same error tomorrow?)

Based on [MS site](https://technet.microsoft.com/en-us/library/bb232205(v=exchg.160).aspx), this is throttling setting to limit "The maximum number of messages per minute that can be sent by a single source". So I tested using powershell script (not sure whether it does matter, so I include the partial code below):

```
$SMTPClient = New-Object System.Net.Mail.SmtpClient( $emailSmtpServer , $emailSmtpServerPort )
$SMTPClient.EnableSsl = $true
$SMTPClient.Credentials = New-Object System.Net.NetworkCredential($emailSmtpUser , $emailSmtpPass );
#[System.Net.ServicePointManager]::ServerCertificateValidationCallback = { return $true }
$SMTPClient.Send( $emailMessage )

```

In this script I'm first submit the email with another user ID, and the result: I'm able to submit email to the same receiver more than 5 times within a minutes. So why does the limit not applied to this case?

After that, I tried the script with my application ID, the same error (4.4.2) prompted. I then checked the tracking log explorer and I found there is no other email submitted with that application ID. So is it Exchange store the user count some where which I need to reset it? And how can I trace the email submission? It doesn't seem appears in tracking log explorer, so as my concern earlier, it might hit the same error even I change it to 50, I'm unable to troubleshoot further without able to trace them.

Sorry as the question is a bit long.

Appreciate if anyone can provide me some clues.