I personally use Google Apps for all my email needs. The basic plan is free and spam filtering is top notch. I also love the free POP/IMAP access and the fact that they do not add little text adds to the end of my outgoing messages.

Thanks for the replies, webmail.us looks like a pretty good option. Any idea how good their spam filtering is?

I setup tuffmail for a relative’s office (three people). Along with FastMail.FM, webmail.us, and FuseMail, tuffmail seems to be among the top recommended mail providers. My research mainly consisted of sifting through discussions on http://www.emaildiscussions.com/, some googling, and comparison of the various feature sets offered. I ended up with tuffmail because it was possible to get lower pricing by sacrificing some disk space (which wasn’t needed, since the users all regularly download their mail via POP into a custom client application). During the trial period I was pleased with the provided ability to customize which anti-spam measures would be used. In fact, the help page for that functionality proved useful when I configured postfix and SpamAssassin on our slice.

Matt, I will look into it. It appears I have a lot of good options. Thanks for the input everyone.

I have been running Communigate Pro by Stalker.com for the better part of 6 years.

They used to be less expensive, but the most rock solid SMTP server I have ever seen.
There web interface is quite amazing.

They have a "community" version which is free and supports one domain and I think either 5 or 10 accounts.

Spam filtering on webmail.us is very decent. Not as good as Google, though. But at least I've never gotten any phone calls from my clients about email not working.

I did try fusemail for a few days but I gave it up. The control panel and the way everything is set up just gives you that constant sense of "this is not yet done and shouldn't be live yet" and I found it totally confusing for even the simplest email setups. I mean, for G-d's sake, the reseller welcome email and PDFs contained incorrect and outdated information. I just... nothing was where it should've been in that system.

PS: I'm biased, I admit it. Out of my low $xxx activation fee (which was non-refundable) and $99 first month's prepayment (which said nothing about being non-refundable), they refused to even refund the $99 when I terminated early as per the specially negotiated exit clause. So they kinda left me with a bad taste. Oh well, somebody got 1/4 iPhone with that.

I've been using Tuffmail for my personal and business email for 2 years, and have set up and configured accounts for clients ranging from 1 user to 25 users. Highly recommended!

There's been some mention of Zimbra and its competitors, here are comparisons between many of them and a zimbra hosting provider, showing:

Fusemail vs. Zimbra hosting,

Zimbra host versus Exchange host,

Google Apps compared to hosted Zimbra

I work in R&D at a company that produces email/communication networks. Zimbra is what we use internally,
coupled with our own anti-spam/malware software. We're pretty happy with it, and the rich client works rather well on an iPhone :-)

Try mailpicker.com You will able to manage all your mail in one place. I already love it!