Want to access your AOL or Outlook.com mail via Yahoo! Mail? Yahoo's got you covered.
The deliverability consultant in me wonders exactly how this is accomplished. It might be that only the inbox folders come across and you probably don't get a chance to see anything in your AOL or Outlook.com spam folder. I find a fair number of false positives in my Gmail spam folder; but that doesn't mean that the same would be true of AOL or Outlook, or even of the Gmail spam folder for other regular joe users, who aren't email nerds like we are.