I had major problems with Yahoo, but I too had signed up with a .com from them and was getting over 300 spam emails a day. After switching to Gmail and getting rid of my .com, I set up a second email account, that I called Spam. I use this account (with a username very similar to my actual one) to sign up for things online that I need to provide an email address for. If this account ever gets out of control, I can delete the account without worrying about people not being able to contact me.
In regards to the fact that as long as the email is in your address book all is well, true. But this conversation originated from a discussion about job offers being sent by employers to freelancers. In this case, many times their email address is not in your address book. For someone who is constantly working freelance, or working with different designers, directors, actors, etc. , this can be difficult to do.
My best advice to those dealing with spam- make sure that on resumes you have a telephone and email address. Remove the bad email account completely (don't just stop checking it, actually delete it) and set up 2 accounts (Gmail is my preference). 1 account for your actual mail, and 1 account to use when signing up for things online. Do NOT let your email address get published anywhere online whatsoever. Do NOT list it on a website. If you must have email on your website, use a dummy email address and then forward those to your actual email. This way you can change it often, but DO NOT let your primary email get out there to the public.
That's my two cents. This comes from months/years of being absolutely furious about the amount of spam I was getting and the amount of legitimate emails I was losing on a daily basis.