SBS 2011 sends daily/weekly/instant reports from the account SBSMonAcct@. It uses localhost as the SMTP transport as being SBS Exchange is usually installed.
I want to use an external SMTP server. Where can I change these settings?
I don't think that you can. I think it's hard-coded.
I have SBS08, not SBS2011, but apparently they both use the
Windows SBS Fax Sharepoint Receive Connector for the SBS console mail. This is set to allow all connections from 127.0.0.1 anonymously.
Your best bet would probably be to set up some kind of SMTP server with similar properties, perhaps the one that came with IIS7?
(I can't test this because I have 2008 and Exchange, but it might be worth a shot.)