SBS POP3 Connector - Message Exceeds Maximum Message Size

We recently set up a new server for one of our customers using SBS 2011. Simple set up, everything you need in the console and all pretty self explanatory. Superb! However, a week later, we had a strange call from the customer explaining that some of their mail wasn't being delivered. Odd. Upon further inspection, and finding the awfully placed Exchange logs (Some are in Microsoft > Exchange under Applications and Services, however the actual useful information was coming up in the Windows Small Business Server 2011 section... Microsoft making it easy for us as ever...).

I did, however, find this message:

Event ID 210

One or more of the messages (message number) were left in the ‘[accountname]‘ account on the POP3 Server ‘[servername]‘ because they are larger than the maximum acceptable message size (the largest message is [messagesize] bytes). You can either connect to the POP3 account and retrieve or delete the messages manually, or increase the maximum acceptable message size in Exchange Server.

The problem was that some messages, ranging in size from just over 10mb to just under 15mb were too big to be downloaded. So I did some digging, tried changing the Transport settings, however, the real solution is actually very simple, if not immediately obvious.

Exchange sets a default maximum message size of 10mb for downloading, but it is not just the connecter that is being used you need to change, it is several.

“Windows SBS Fax Sharepoint Receive [servername]”
“Windows SBS Internet Receive [servername]”
“Default [servername]” 

Now, you need to change the maximum message size for all three of these connectors using the Exchange Management Shell and the following command:

set-receiveconnector “Windows SBS Fax Sharepoint Receive [servername]” -maxmessagesize 20mb

Once you have done this for all three of those Receive Connectors, you will find that your mail will download as long as the new limit is high enough. And don't make the same arrogant mistake I did of saying "Of course I don't need to do all three, I'll just change my actual mail connectors and ignore the Fax connector". You do.