I echo boe777's advice; my primary (ISP provided) mail address is only used for contact with close friends and family and in the ten year's I've owned it I've had only one item of spam. My other two mentioned mail addresses both exist for specific purposes, have a consequent small circle of receivers, and have never been spammed.
For all my online shopping I use another dedicated mail address and for forum membership another. Both of these are web-based. The online shopping account receives probably 10 items of spam a day and the forum one none, but either can be thrown away at the drop of a hat if spam becomes a nuisance.
Of course with on line shopping I look for the option to switch off authorization for further mail address usage, but one thing I am always careful to do with forums is to switch off any means of Joe Public (and web crawlers) finding the mail address too. Sometimes this can be done during registration, but if no option is given I always go back and look for it directly afterwards in "manage my account" or whatever.