If you run the Best Practices analyzer (BPA) on your SBS 2011 server, two warning messages about a conflict in the MaxMessageSize between the Exchange Transport and the Exchange Send/Receive Connectors. Here’s what the BPA warnings look like:

And if you click on each of them, you will see a detail view:

Since they are only warnings, you could simply ignore it by clicking on the “Exclude the Result” button for each. But, fixing these warnings is a fairly simple process. More importantly, fixing them will get you better acquainted with Exchange PowerShell. Oh, and one final note: these same commands will work on an SBS 2008 server.
So, let’s get going!
Step 1: Start up Exchange PowerShell
Click Start –> Microsoft Exchange Server 2010 –> Exchange Management Shell

Give it a few moments to initialize. Once done you will have a black window with a command prompt.
Looks pretty much like the DOS Command Prompt window, doesn’t it?

Step 2: View current settings
Now we need to type in three PowerShell commands in order to view the current MaxMessageSize values:
- get-receiveconnector | ft name, maxmessagesize
- get-sendconnector | ft name, maxmessagesize
- get-transportconfig | ft maxsendsize, maxreceivesize
Note: the symbol before ft is commonly called the pipeline (|) symbol.
It’s located on the backslash (\) key on most keyboards.
Here’s the result of those three commands on my server:

In my case, my Receive and send connectors were all set to 10MB maxmessagesize, but my transport maxmessagesize was configured as unlimited. So, I had to ask myself: what do I want to change?
Step 3: Change MaxMessageSize settings
I decided that I wanted to change everything to to a 30MB maxmessage size. So, here are the commands to do that:
- set-transportconfig –maxreceivesize 30MB –maxsendsize 30MB
- set-sendconnector “Windows SBS Internet Send SBS1” –maxmessagesize 30MB
- set-receiveconnector –identity “Windows SBS Internet Receive SBS1” –maxmessagesize 30MB
- set-receiveconnector –identity “Windows SBS Fax Sharepoint Receive SBS1” –maxmessagesize 30MB
- set-receiveconnector –identity “Default SBS1” –maxmessagesize 30MB
Here’s a screenshot of entering those commands on my server:

Step 4: Verify Changes
Rerun the three commands from Step 2 and verify that all maxmessagesize values match!

Now, rerun BPA and those two warnings should be gone!
Finally, for more information, you may wish to refer to the Microsoft blog post on this same topic.