This has been discussed elsewhere, but no solutions have been posted and some of the advice is flat wrong. I crowdsourced this problem on my own forum/twitter, and this is what I've learned so far. 1. Connecting to Yahoo Mail is a simple procedure, and following the imap4/smtp directions here will work. 1b. However, step 1 (enter your username) MUST be with firstname.lastname@example.org, not just X. The default the android offers will fail. 1c. If it doesn't load, or the folders don't load, power down and then back up. For people who find it "hangs" (little circle at top left keeps spinning)-- delete the account off of the android and set it back up. I have tried this on literally dozens of phones, it works just fine. But: 2. The multiple copies in the sent folder is a serious problem that I cannot fix. TURNING OFF THE SENT FOLDER ON YAHOO DOES NOT WORK-- and this is what amazes me; the Android is somehow able to override Yahoo mail and force copies into the sent box. If you send an email from your desktop, nothing is saved; but sent off the Android and the copies begin. 2b. The copies are generated each time the Android connects to Yahoo to check for mail (this is pull, not push), and whenever you send an email, and whenever you hit refresh. It seems to do it two copies at a time (why?)-- so if I send mail A, it generates two copies. When I send mail B, it generates 2 more copies of A, and 2 copies of B. When I send mail C, then we're up to 6 As, 4 Bs, 2 Cs, etc... I've tried multiple solutions, and have not been able to fix this.