Thanks Josh!
So just to check I've understood...
If I set up the smart campaign with a single trigger for Email Bounces, with conditions of Is Any and Min Num of Times 2, the following will apply?
Lead has not bounced before and bounces for the first time --> not triggered
Lead has bounced once before and bounces for a second time --> triggered
Lead has bounced twice or more and bounces for a third or subsequent time --> triggered
In which case, cool - a simple trigger, no filters needed. (Take your point that it could be a batch campaign instead, and will take a judgement on that as a next step.)
Thanks very much!