The Spam Protection slider on the settings page is all the controls most people need to set up or change their spam protection!
New accounts start out with their slider set to Standard. This starts off holding all mail. We also recommend setting up your email program to send mail through Pobox; that way, we can make everyone you send mail to a Trusted Sender!
After a few weeks, your Trusted Sender list should be fairly extensive. At that point, you can switch to the setting most Pobox staffers use -- Aggressive. This automatically bounces all the most likely spam, and only holds things we're less sure about. You can also change your emailed report to only include Held messages at this point.
If most of your correspondents live in the same countries, you may also want to turn on Country Blacklisting, which is directly under the spam slider. Select countries or whole continents!
If you still use custom settings, we strongly recommend upgrading to one of the Pobox Recommended groups. Many of the old blacklists are dying, or are no longer as accurate as they once were. Some of the old options available in custom settings misidentify as many as 1 in 10 messages. We recommend making the switch to the recommended groups. They are managed by accuracy, so your settings are set to match your accuracy comfort level, rather than a fixed list of blacklists.