So what you all may not know is that I am a digital.forest customer, and have been for quite some time. This blog and my email accounts are hosted through them, and I have to say, they have been nothing but excellent from a QoS and support POV. In fact, I would almost rather take down the site than switch ISPs.
They also are, quite by accident, a very iPhone - Friendly email provider for a couple reasons:
First, their primary anti-spam method is Postini. Postini works, (and damned well mind you), by intercepting the mail before it gets to the mail server. The server doesn't have to deal with it. It's really effective, and instead of deleting it, it just holds it. False positives, (of which there are few), are easily dealt with via a simple Web UI. So for me, I've had no real spam issues on my iPhone. In fact, there's been a zero increase in spam on my iPhone vs. any other client, because it's all handled well before it gets to the server, much less the client. So spam? Not a problem.
Secondly, the mail server they use has a basic UI for setting up server-side rules. (By "basic" I mean, "really poorly - designed crap UI that only an email server programmer could love), but it DOES work. So all my mail on those servers can be filtered before I ever even connect.
This was not something that d.f. intended, it just happens to work that way. Luckily, that makes for a really pleasant iPhone email experience. If you are looking for a better email provider for your iPhone, check out d.f.