Msgpush.com is a new web service that takes advantage of the iPhone 3.0 software to offer instant alerts on the iPhone when email arrives in your inbox.
When the iPhone was first released, there was a lot of hype about it offering true push email on the go for users. Everyone hoped that this would be provided through the IMAP IDLE extension, which would have made the feature available to all IMAP email services that support IMAP IDLE.
In fact, it turned out that this service was available first of all only to Yahoo.com mail users, and then later in the iPhone 2.0 software to Exchange users, and it doesn’t use IMAP IDLE.
The best my iPhone can do is poll my IMAP accounts through its “Fetch” feature every fifteen minutes.
Hoping to overcome this limitation, msgpush.com offers iPhone users the option to receive faster notification of new email by providing each user with a “fake Exchange account”.
Here’s how it works: You sign up at msgpush.com. It monitors your IMAP account through IMAP IDLE, and then sends notification of new mail to your iPhone through the Exchange protocol. Sounds clever, but there are some caveats:
- You need to surrender your username and password for the IMAP account to msgpush.com, which not everyone will feel comfortable about.
- You need to set up a new Exchange account on the iPhone to receive these notifications. But Exchange only allows you to run one profile at a time. So, if you have one configured already (as I do for my Zimbra account at work), this service is a non-starter.
- It doesn’t actually read or push the email itself, only a notification that the email is waiting in your account’s inbox. So you still need to retrieve the email manually.
- It’s still in beta and, according to some users, is proving a little erratic.
Still, even with these quibbles, it may be the solution that some users who can’t wait fifteen minutes are looking for.
I haven’t tested it (see 2. above), but you might like to. Sign up 
at the msgpush.com web site.
[With thanks to the Fastmail blog and forum posters ]
UPDATE: Tom Yager writes more on push email and the iPhone 3.0 software at InfoWorld.
I have tried this numerous times in the past week and haven’t been able to get gmail to work. I provide my gmail credentials and get:
Could not connect and/or authenticate. [ALERT] Web login required (Failure)
That’s bad luck. According to a poster on the Email Discussions Board, push, or at least Exchange ActivSync, is coming to Gmail soon:
http://www.emaildiscussions.com/showpost.php?p=482198&postcount=3
Ugh. Not to be a jerk, but this is why I continue to use a Blackberry for my Gmail and IM.
I pay money to my carrier to get rock solid messaging (and Google Maps). Meanwhile, all the great things about the iPhone OS are right there on my iPod Touch, without the monthly fee.
What are the advantages of setting up a Zimbra account on the iPhone as an Exchange account? Zimbra’s email is IMAP and the calendars work just fine when subscribed as CalDAV.
Another approach to mail notifications is the iPhone app Prowl, which works in conjunction with notification system Growl.
Depending on the interval you set on your home Mac to check mail, it works pretty instantly. You only get notices currently, but the developer said the next version should support opening specific apps on your iPhone depending on the message received.