Can't seem to filter using SearchCondition for a specific combo

[Shogan]

Try as I may, I can't seem to filter out this criteria:

Messages should be:

• Unseen
• To a specific address
  Not contain "offer", "offered", "wanted" or "taken" in the subject line.

I've tried various combos, this is my latest attempt, which didn't work either:

var catchAll = ic.SearchMessages(SearchCondition.Unseen()
.Not(SearchCondition.Subject("offer")
.Not(SearchCondition.Subject("offered")
.Not(SearchCondition.Subject("wanted")
.Not(SearchCondition.Subject("taken"))))).And(SearchCondition.To(mainAddress)));

My other filters which are also fairly complex (but don't use "Not") all work perfectly though. Am I doing my SearchCondition above wrong?

[Shogan]

Feel free to close this, I couldn't get a long list of nested conditions working nicely, so I ended up just creating my own matching methods with regex after doing an initial filter for SearchCondition.Unseen and SearchCondition.To. I then simply iterate the results of the above two search conditions and do my own nested checking on the subject / bodies of remaining messages in the result array.