It's a mental resource hog if nothing else. Just changed a setting on my moms phone and noticed she had 108k unread emails between two accounts. All spam.
I got locked out of a Yahoo account years ago that I used solely as a spam account for signups. It was getting hundreds a day and I just looked for that one email confirmation as necessary. Sometimes I wonder if it's still active. It might have a million emails waiting (were Yahoo to allow unlimited messages).