Ok, can't flaw the result, that works fine, accounts@ is showing as the To: header, and I assume the scalix rules will work on that and hence filter nicely.
I can pick some big holes in the method though, just feels like the wrong way to do things. Is this a bug, or part of the deliberate 'feature' where you can only send from the primary email address? Because at the moment it does merit asking the question as to what the point of addition email addresses is?
Will reconfigure all this way, just hope I can sell this 'method' in the mean time as we've got at least 2 clients begging for something like this, at this pricepoint.