I have been using the Yahoo mail for last 6 years or so. Previously Yahoo mail had the folder named bulk mails and I used to get 100s of bulk mail during the recent times. When Yahoo mail beta was launched I too moved on to the latest version. This version has the folder called spam instead of bulk mails. I never used to check the bulk mails, until the folder was renamed to spam.
Now the question is how does Yahoo mail classify mails as spam? I have been randomly checking the spam mails and recently I found out that many of the mails sent from my friends have gone to spam folder! The interesting catch in this is that these mails were sent from Gmail Ids. Further, the approval mail from Google Adsense, when I joined Adsense, also went to spam folder and infact I was wondering why there was no reply from Google about my application status.
Still no idea how those were mails were treated as spam. Is it because of the presence of too many links in the mail or is it because of the names of the senders? But now I make it sure that I go through spam mails before I delete them.