Yahoo mail won't push to my iphone and iPad

Actually Yahoo does use Apple's push notification. It's basically the only one to do so other than iCloud which is why Yahoo was the first email provider to support push on the iPhone. All the other ones use the Microsoft Exchnage mechanism. I have the Netstat app installed and when I send myself a test message to my Yahoo account, I can see that there is a burst of traffic on the connection to Apple's push server (push.apple.com). That triggers the mail app to check for mail. If the mail app wasn't downloading mail, that would be a Yahoo problem. This is how I can tell if there's a push issue or a mail check issue. Currently when I send myself a test message, there's no traffic across the Apple push server connection so I know there's no push occurring. When I implement the work around (add the extra Yahoo account), the push activity occurs again and push mail starts working.

It's possible it's a Yahoo issue since Yahoo might not be sending the new mail notification via Apple's push system, but that doesn't explain why adding another Yahoo account causes pushes to be sent for a completely different device. The only thing I can think of is that Yahoo knows both accounts use the same UUID and that registering the other account "activates" the UUID somehow. Otherwise it's a problem on Apple's end.

I ended up calling Apple support and a senior person couldn't figure out what's wrong. They said it's like a Yahoo server issue since it's happening on 2 different devices, but if I want to escalate I'd have to do a restore on one of my device (which I'd rather not do as it's time consuming).

iOS always had a push server, it just wasn't open to apps (since there weren't any). Yahoo has had access to the push server since the iPhone was released. Originally push only worked over 3G, but Apple fixed this later on to work over WiFi. That's also why Yahoo push mail didn't used to work on any device except the iPhone and iPad 3G.

Yahoo is partnered with Apple to provice push notifications. Yahoo push is actually integrated into iOS as opposed to other email providers, which need to use Microsoft Exchange. That's why none of the other built in email providers provide push without having to manually add them. For example to get push with Gmail, you can't just choose to add a Gmail accout, you need to add a Microsoft Exchange account and put in Gmail's servers.

Again it could be a Yahoo problem, but it could also be an Apple problem or a miscommunication between the two. In my case, it's only one of my accounts that won't work with push and only if it's the only Yahoo account on the device with push active. If there's another Yahoo account with push active, then push will work on that account as well.

I'm not arguing with you on how Yahoo push works on the iPhone since I've spent a lot of time studying it. I know how it works as I've mapped the actual network traffic. There is no contact to the Yahoo servers prior to the mail app trying to download mail. All traffic goes through Apple's servers prior to that, just like a MobileMe/iCloud mail push.

It sounds like you have a basic understanding of network principles, but are slightly confused so let me make this really simple. Here's how Yahoo Mail "push" works and how it's always worked since iOS 1. I put "push" in quotes as it's really a commanded fetch.

1. A new message appears in the Yahoo Inbox.

2. Yahoo! sends a message to Apple (it likely doesn't use the same Push API that apps use, but a special notifcation designed for Yahoo.

3. Apple sends out a notification to the device which triggers the Mali app to check for new mail.

4. The app checks for mail the same way it does when opening the Mail app or pressing the refresh button. If you actually have the app open, you'll see it just start checking for mail on it's own. If there's new mail it will download it (sometimes it fails *). Yes it uses the imap.apple.mail.yahoo.com server, but there's nothing special about that. You can manually specify to use imap.mail.yahoo.com and that will work as well, though push will stop working after a while with that set up.

So basically Yahoo Mail isn't pushed, it's fetched, but the fetch is triggered by a notificaiton. Yahoo does not use the IMAP IDLE since the phone does not leave open a constant connection to Yahoo's IMAP server.

Some things have changed since iOS 1 namely that the Yahoo account on the phone now logs in using a user name and password instead of a hash cookie and also that Yahoo now supports IMAPS (it used to only support IMAP), but the basic push system is the same.

(*) - I mentioned that sometimes mail fails to download. This happens when Yahoo indicates there's new mail to download, but for whatever reason the mail never downloads. When this happens, the Mail app on the phone won't actually sync with the Yahoo Mail server. Even though the "push" notification worked, mail won't actually download. This persists until the state of the Yahoo Inbox changes, so manually refreshing won't work (which I believe it a bug in the iOS IMAP implementation since no other IMAP clients have this problem). That's how one can tell the difference between a "push" notification issue and a "fetch" problem. I was actually having this problem a lot a few weeks ago, but it cleared up. I