I'll admit to having never used Incredimail. I looked at the product page for it, and left very quickly after realizing it was designed in the Fisher Price style. Lots of cute animations full of bright pastels, which serve absolutely no purpose at all.
Anyway, sparing you all the boring technical details, not all email programs store messages in the same way. It's entirely possible Incredimail uses a system that doesn't use the whole compacting thing. Even on programs that do use that storage method, you save so little space by compacting, it's not really worth it. It's a feature left over from the days when hard drives were in the 20MB range, and every little bit of space counted. In the days of multi-GB drives, we can afford to be a little wasteful.
Does anyone know how to compact files in Incredimail?
I would appreciate any advice