Exchange – Maximum Message Size for High Priority Emails

You may want to change the maximum message size for high priority emails, as the default value is 250KB. The “MaxHighPriorityMessageSize” parameter controls the maximum allowed size for a high priority message.

Navigate to the Bin directory and find EdgeTransport.Exe.Config file. Open it using notepad and find the line that says MaxHighPriorityMessageSize:

Change the value of “MaxHighPriorityMessageSize” from 250KB to the one of your choice, let say 5MB. You should get something like this:

If a high priority message is larger than the value of the “MaxHighPriorityMessageSize” parameter, the message is automatically downgraded from high priority to normal.