So now that the iPhone's been available for a little over 24 hours, folks are finding out that its email capabilities will take a bit of getting used to. Ideally, whatever you do to your email via the iPhone should be reflected when you access your email via a web interface or via a desktop client (mail.app, Outlook, etc.). However, that's not always the case with the offerings available right now. Here's a run-down of the major drawbacks of each major iPhone email provider:
Yahoo is a strong contender for best email service as it's the only one that implements the IMAP IDLE functionality, giving the iPhone a light-weight push mail capability like the one that makes Blackberries so addictive. As soon as Yahoo's email servers receive a new email they ping your iPhone. Unfortunately, you can only access your email via the web or the iPhone for free; if you want to also work with that email via a desktop client you'll need to pay $20/year to gain POP access. You can't get IMAP access, so that means that any email you send via the iPhone or web will not get added to your desktop client's "Sent Mail" folder—this is the big drawback of POP email.
Gmail is currently my primary email provider, and I've been quite happy with both its performance and its generous storage limits. However, it only provides POP access to desktop clients and the iPhone, so the POP sent mail problem exists here as well. Even more frustrating, though, is that Gmail automatically puts a copy of every email you send into your inbox as well as the "Sent Mail" folder. The result is that you have to delete a copy of every email you send via the iPhone to get it out of your inbox. This introduces too much overhead into the act of sending email from the iPhone and makes Gmail quite unattractive. And that's not all: The first time you setup your Gmail account on the iPhone, the iPhone will download a copy of every email you've ever sent unless you clean up the "All Mail" folder first. And, with no way to select multiple messages to delete on the iPhone you may get to practice deleting emails several hundred or thousand times to clean up your iPhone's inbox.
.Mac offers 1 GB of email storage, along with an online address book and calendar that syncs with those OS X apps, and other related functionality, for $99/year. This price makes .Mac the most expensive email option, but it also provides IMAP access to both the iPhone and any IMAP desktop client. It also has a pretty good AJAX-based web interface, making .Mac the first email provider we've looked at that offers most of the IMAP functionality we've been looking for. Unfortunately, .Mac doesn't offer push mail, so you still have to wait for the iPhone to poll .Mac to find out if you have any new email. Also, all of the related pieces of functionality beyond email that make the annual price somewhat more reasonable are not available for Windows users, as they rely on OS X functionality. A free 60-day trial is available.
AOL offers free IMAP email with a decent AJAX web user interface, 2GB of email storage, address book sync via Plaxo, and support for Outlook calendar syncing. Aside from not offering push mail, what's not to like? Well, you do get bombarded by ads when using the web user interface, and to some there's a stigma to having an "@aim.com" email address. Also, this service doesn't do a good job of advertising its functionality and the help files are minimal compared to the other services, so it makes you wonder how well they'll support the iPhone if problems crop up.
Right now there isn't a single, ideal email provider for everyone. Yahoo could be the one if they'd open up an IMAP interface to desktop clients, something that they've toyed with in the past. However, until they do that, their push mail functionality isn't enough to put them at the top. The best option appears to be .Mac for Mac users, and AIM Mail for Windows users, as both of these services provide both IMAP access and web-based access.