Recs.
Updated
Fastmail is a personal and business web-based email service with support for IMAP, SMTP and XMPP.
SpecsUpdate
Pros
Pro Traditional revenue model increases likelihood of personal data privacy and safety
Depending on your point of view, requiring to pay for Fastmail is actually a positive aspect of the service. This way you know the company is at least making some revenue (they have been around since 2010) and you know who the customer is. Pricing is as follows (go here for their on-site pricing info).
Pro Adjustable spam filter
On writing this Fastmail has Basic, Normal, Aggressive or Customisable spam filtering which can be selected in the Advanced settings.
Each user has an individually trainable bayes database to improve spam filtering. You can train your personal bayes database by selecting some messages and using the Report spam and Report Non-Spam options from the Action menu on the Mailbox screen.
For IMAP users who don't use the web interface much, you can specify folders as spam/non-spam training folders on the Folders screen. Then just move messages into those folders as appropriate to train your bayes database.
For your personal bayes databases to be active, you have to train it with at least 200 spam messages and 200 non-spam messages. If you haven't trained enough messages, then we use a global continuously updated bayes database against your incoming messages, which helps detect spam/non-spam, but isn't as good as a personally trained one.
Pro Offers subdomain addressing
Instead of using plus addressing (e.g. foo+bar@email.com), FastMail offers the ability to receive mail through subdomain addresses (e.g. foo@bar.email.com).
Pro Identities & aliases practically gives you a new email that you can manage from a single account
With identities and aliases, you can set up a completely new email address that can be managed from your account, without paying for more. As of time of this writing, FastMail offers up to 500 identities and 600 aliases per account, regardless of plan type.