We were receiving following event on our HUB/CAS server and email flow stopped when MSExchangeMailSubmission reached its threshold 40. Is it possible to increase the threshold and how?  Thanks in advance !

Log Name:      Application
Source:        MSExchangeMailSubmission
Event ID:      1010
Task Category: MSExchangeMailSubmission
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      CAS0
Description:
The hub server CAS0 is currently processing 40 submissions, which is the maximum allowed.

Hi,

From your description, I would like to clarify the following things for troubleshooting:

1. Please run Exchange Troubleshooting Assistant to check the Exchange server performance and mail flow.

2. You can go to the bin folder on Exchange server, backup "EdgeTransport.Exe.Config" file and add or modify the following line with changing the value accordingly in appsetting section.

<add key=MaxConcurrentSubmissionsPerHubServer value=40>

Hope this can be helpful to you.

Best re

Thanks Amy for your reply. We couldn't replicate the problem currently. But the CPU and RAM usage were low when that happened. We are not sure how much we could increase the value of MaxConcurrentSubmissionsPerHubServer since we are afraid of it could overload the server. Do you have any recommendation ?