Hiding your IP address only helps so much.
The problem is when you get on anyone's mass email list. If they don't use BCC, it only takes one errant computer on the mailing list, and then everyone is both implicated in spamming, as well as a recipient of spam.
The only way to conquer that is to make sure no one uses CC on email or separates multiple email addresses in the to field. Both of these are ripe harbingers for spam.
When you hide your IP, you also make it harder to login websites you want to connect to for keeping account records of when you purchased things at specific stores.
Some people use a throw away email address for the outside world, and people they want to contact who won't spam them they give a better unique email address.