Loss of gain change on export

I have a project with 16 tracks, each with different gain levels (as set on each of the left hand tool boxes of each track), yet when I export to MP3, those volume differences do not transfer. For example there is one track that would normally dominate the others and I have set the volume very low on the project, but when all the project is exported, that track is still very loud. When I play the aup file its sounds as it should.

Please help – I am very new to Audacity!

Thanks!

You adjusted your volumes with the sliders to the left of each track, right?
Koz